| IRS990/AccountantCompileOrReviewInd | 0 | 0 |
| IRS990/AccountsPayableAccrExpnssGrp/BOYAmt | 0 | 1651972 |
| IRS990/AccountsPayableAccrExpnssGrp/EOYAmt | 0 | 2054139 |
| IRS990/ActivitiesConductedPrtshpInd | 0 | 0 |
| IRS990/ActivityOrMissionDesc | 0 | WINDWARD IS AN INDEPENDENT CO-EDUCATIONAL DAY SCHOOL FOR GRADES 7 TO 12. |
| IRS990/AdvertisingGrp/ManagementAndGeneralAmt | 0 | 241 |
| IRS990/AdvertisingGrp/ProgramServicesAmt | 0 | 141456 |
| IRS990/AdvertisingGrp/TotalAmt | 0 | 141697 |
| IRS990/AllOtherContributionsAmt | 0 | 3654872 |
| IRS990/AllOtherExpensesGrp/FundraisingAmt | 0 | 51304 |
| IRS990/AllOtherExpensesGrp/ManagementAndGeneralAmt | 0 | 16927 |
| IRS990/AllOtherExpensesGrp/ProgramServicesAmt | 0 | 148368 |
| IRS990/AllOtherExpensesGrp/TotalAmt | 0 | 216599 |
| IRS990/AnnualDisclosureCoveredPrsnInd | 0 | 1 |
| IRS990/AuditCommitteeInd | 0 | 1 |
| IRS990/BooksInCareOfDetail/BusinessName/BusinessNameLine1Txt | 0 | STEVEN KIERMAN |
| IRS990/BooksInCareOfDetail/PhoneNum | 0 | 3103917127 |
| IRS990/BooksInCareOfDetail/USAddress/AddressLine1Txt | 0 | 11350 PALMS BLVD |
| IRS990/BooksInCareOfDetail/USAddress/CityNm | 0 | LOS ANGELES |
| IRS990/BooksInCareOfDetail/USAddress/StateAbbreviationCd | 0 | CA |
| IRS990/BooksInCareOfDetail/USAddress/ZIPCd | 0 | 90066 |
| IRS990/BusinessRlnWithFamMemInd | 0 | 0 |
| IRS990/BusinessRlnWithOfficerEntInd | 0 | 0 |
| IRS990/BusinessRlnWithOrgMemInd | 0 | 0 |
| IRS990/CashNonInterestBearingGrp/BOYAmt | 0 | 14917965 |
| IRS990/CashNonInterestBearingGrp/EOYAmt | 0 | 10488646 |
| IRS990/ChangeToOrgDocumentsInd | 0 | 0 |
| IRS990/CntrctRcvdGreaterThan100KCnt | 0 | 1 |
| IRS990/CollectionsOfArtInd | 0 | 0 |
| IRS990/CompCurrentOfcrDirectorsGrp/FundraisingAmt | 0 | 57093 |
| IRS990/CompCurrentOfcrDirectorsGrp/ManagementAndGeneralAmt | 0 | 392731 |
| IRS990/CompCurrentOfcrDirectorsGrp/ProgramServicesAmt | 0 | 485261 |
| IRS990/CompCurrentOfcrDirectorsGrp/TotalAmt | 0 | 935085 |
| IRS990/CompensationFromOtherSrcsInd | 0 | 0 |
| IRS990/CompensationProcessCEOInd | 0 | 1 |
| IRS990/CompensationProcessOtherInd | 0 | 0 |
| IRS990/ConferencesMeetingsGrp/FundraisingAmt | 0 | 3787 |
| IRS990/ConferencesMeetingsGrp/ManagementAndGeneralAmt | 0 | 150 |
| IRS990/ConferencesMeetingsGrp/ProgramServicesAmt | 0 | 165555 |
| IRS990/ConferencesMeetingsGrp/TotalAmt | 0 | 169492 |
| IRS990/ConflictOfInterestPolicyInd | 0 | 1 |
| IRS990/ConservationEasementsInd | 0 | 0 |
| IRS990/ConsolidatedAuditFinclStmtInd | 0 | 0 |
| IRS990/ContractorCompensationGrp/CompensationAmt | 0 | 340560 |
| IRS990/ContractorCompensationGrp/ContractorAddress/USAddress/AddressLine1Txt | 0 | 11511 BARMAN AVENUE |
| IRS990/ContractorCompensationGrp/ContractorAddress/USAddress/CityNm | 0 | CULVER CITY |
| IRS990/ContractorCompensationGrp/ContractorAddress/USAddress/StateAbbreviationCd | 0 | CA |
| IRS990/ContractorCompensationGrp/ContractorAddress/USAddress/ZIPCd | 0 | 90230 |
| IRS990/ContractorCompensationGrp/ContractorName/BusinessName/BusinessNameLine1Txt | 0 | ALPHA BUILDING MAINTENANCE |
| IRS990/ContractorCompensationGrp/ServicesDesc | 0 | FACILITY SERVICES |
| IRS990/CreditCounselingInd | 0 | 1 |
| IRS990/CYBenefitsPaidToMembersAmt | 0 | 0 |
| IRS990/CYContributionsGrantsAmt | 0 | 3654872 |
| IRS990/CYGrantsAndSimilarPaidAmt | 0 | 2179557 |
| IRS990/CYInvestmentIncomeAmt | 0 | -144821 |
| IRS990/CYOtherExpensesAmt | 0 | 9007816 |
| IRS990/CYOtherRevenueAmt | 0 | 2650192 |
| IRS990/CYProgramServiceRevenueAmt | 0 | 21547552 |
| IRS990/CYRevenuesLessExpensesAmt | 0 | 1199367 |
| IRS990/CYSalariesCompEmpBnftPaidAmt | 0 | 15321055 |
| IRS990/CYTotalExpensesAmt | 0 | 26508428 |
| IRS990/CYTotalFundraisingExpenseAmt | 0 | 816157 |
| IRS990/CYTotalProfFndrsngExpnsAmt | 0 | 0 |
| IRS990/CYTotalRevenueAmt | 0 | 27707795 |
| IRS990/DecisionsSubjectToApprovaInd | 0 | 0 |
| IRS990/DeductibleArtContributionInd | 0 | 0 |
| IRS990/DeductibleNonCashContriInd | 0 | 1 |
| IRS990/DeferredRevenueGrp/BOYAmt | 0 | 10750720 |
| IRS990/DeferredRevenueGrp/EOYAmt | 0 | 12234801 |
| IRS990/DelegationOfMgmtDutiesInd | 0 | 0 |
| IRS990/DepreciationDepletionGrp/FundraisingAmt | 0 | 64870 |
| IRS990/DepreciationDepletionGrp/ManagementAndGeneralAmt | 0 | 286845 |
| IRS990/DepreciationDepletionGrp/ProgramServicesAmt | 0 | 1151933 |
| IRS990/DepreciationDepletionGrp/TotalAmt | 0 | 1503648 |
| IRS990/Desc | 0 | THE SCHOOL PROVIDES A VARIED AND CHALLENGING ACADEMIC PROGRAM, A WIDE RANGE OF OPPORTUNITIES FOR STUDENTS TO PARTICIPATE IN ATHLETICS, THE ARTS, AND COMMUNITY SERVICE, AND A DIVERSE STUDENT BODY. CLASSES AVERAGE 16 STUDENTS, AND THE STUDENT-FACULTY RATIO IS APPROXIMATELY 8:1.THE SCHOOL PROVIDES EXCELLENT PROGRAMS IN ENGLISH, MATHEMATICS, FOREIGN LANGUAGE, HISTORY, SCIENCE, AND THE VISUAL AND PERFORMING ARTS. THE CURRICULUM OFFERS STUDENTS A CHOICE OF MORE THAN 100 DIFFERENT COURSES. A HIGH PERCENTAGE OF WINDWARD STUDENTS UNDERTAKE ADVANCED PLACEMENT COURSEWORK. ALL WINDWARD STUDENTS ARE REQUIRED TO FULFILL A FORTY-HOUR COMMITMENT OF PUBLIC SERVICE BEFORE GRADUATION.CO-CURRICULAR ACTIVITIES FIGURE PROMINENTLY IN THE WINDWARD EXPERIENCE. FROM ATHLETICS TO STUDENT COUNCIL TO THE PERFORMING ARTS, NEARLY EVERY WINDWARD STUDENT PARTAKES IN OFFERINGS OUTSIDE OF THE CLASSROOM. STUDENTS HAVE THE OPTION OF PARTICIPATING IN A VARIETY OF CLUBS, DANCES, SKI TRIPS AND SPORTING EVENTS THROUGH WHICH THEY DEVELOP STRONG FRIENDSHIPS. THESE ACTIVITIES, COUPLED WITH THE SCHOOL'S ACADEMICALLY RIGOROUS CURRICULUM, HELP TO DEVELOP THE WIDEST RANGE OF STUDENTS' ABILITIES AND INTEREST. |
| IRS990/DescribedInSection501c3Ind | 0 | 1 |
| IRS990/DisregardedEntityInd | 0 | 0 |
| IRS990/DocumentRetentionPolicyInd | 0 | 1 |
| IRS990/DonorAdvisedFundInd | 0 | 0 |
| IRS990/ElectionOfBoardMembersInd | 0 | 0 |
| IRS990/EmployeeCnt | 0 | 253 |
| IRS990/EmploymentTaxReturnsFiledInd | 0 | 1 |
| IRS990/EngagedInExcessBenefitTransInd | 0 | 0 |
| IRS990/EscrowAccountInd | 0 | 0 |
| IRS990/EscrowAccountLiabilityGrp/BOYAmt | 0 | 68322 |
| IRS990/EscrowAccountLiabilityGrp/EOYAmt | 0 | 75662 |
| IRS990/ExpenseAmt | 0 | 23267169 |
| IRS990/FamilyOrBusinessRlnInd | 0 | 0 |
| IRS990/FederalGrantAuditRequiredInd | 0 | 0 |
| IRS990/FeesForServicesLegalGrp/ManagementAndGeneralAmt | 0 | 86091 |
| IRS990/FeesForServicesLegalGrp/ProgramServicesAmt | 0 | 16713 |
| IRS990/FeesForServicesLegalGrp/TotalAmt | 0 | 102804 |
| IRS990/FeesForServicesOtherGrp/ManagementAndGeneralAmt | 0 | 29465 |
| IRS990/FeesForServicesOtherGrp/TotalAmt | 0 | 29465 |
| IRS990/FeesForSrvcInvstMgmntFeesGrp/ManagementAndGeneralAmt | 0 | 26280 |
| IRS990/FeesForSrvcInvstMgmntFeesGrp/TotalAmt | 0 | 26280 |
| IRS990/ForeignActivitiesInd | 0 | 1 |
| IRS990/ForeignFinancialAccountInd | 0 | 0 |
| IRS990/ForeignOfficeInd | 0 | 0 |
| IRS990/Form8282PropertyDisposedOfInd | 0 | 0 |
| IRS990/Form990PartVIISectionAGrp/AverageHoursPerWeekRt | 0 | 1.00 |
| IRS990/Form990PartVIISectionAGrp/AverageHoursPerWeekRt | 1 | 1.00 |
| IRS990/Form990PartVIISectionAGrp/AverageHoursPerWeekRt | 2 | 1.00 |
| IRS990/Form990PartVIISectionAGrp/AverageHoursPerWeekRt | 3 | 1.00 |
| IRS990/Form990PartVIISectionAGrp/AverageHoursPerWeekRt | 4 | 1.00 |
| IRS990/Form990PartVIISectionAGrp/AverageHoursPerWeekRt | 5 | 1.00 |
| IRS990/Form990PartVIISectionAGrp/AverageHoursPerWeekRt | 6 | 1.00 |
| IRS990/Form990PartVIISectionAGrp/AverageHoursPerWeekRt | 7 | 40.00 |
| IRS990/Form990PartVIISectionAGrp/AverageHoursPerWeekRt | 8 | 1.00 |
| IRS990/Form990PartVIISectionAGrp/AverageHoursPerWeekRt | 9 | 1.00 |
| IRS990/Form990PartVIISectionAGrp/AverageHoursPerWeekRt | 10 | 1.00 |
| IRS990/Form990PartVIISectionAGrp/AverageHoursPerWeekRt | 11 | 1.00 |
| IRS990/Form990PartVIISectionAGrp/AverageHoursPerWeekRt | 12 | 1.00 |
| IRS990/Form990PartVIISectionAGrp/AverageHoursPerWeekRt | 13 | 1.00 |
| IRS990/Form990PartVIISectionAGrp/AverageHoursPerWeekRt | 14 | 1.00 |
| IRS990/Form990PartVIISectionAGrp/AverageHoursPerWeekRt | 15 | 1.00 |
| IRS990/Form990PartVIISectionAGrp/AverageHoursPerWeekRt | 16 | 1.00 |
| IRS990/Form990PartVIISectionAGrp/AverageHoursPerWeekRt | 17 | 1.00 |
| IRS990/Form990PartVIISectionAGrp/AverageHoursPerWeekRt | 18 | 1.00 |
| IRS990/Form990PartVIISectionAGrp/AverageHoursPerWeekRt | 19 | 1.00 |
| IRS990/Form990PartVIISectionAGrp/AverageHoursPerWeekRt | 20 | 1.00 |
| IRS990/Form990PartVIISectionAGrp/AverageHoursPerWeekRt | 21 | 40.00 |
| IRS990/Form990PartVIISectionAGrp/AverageHoursPerWeekRt | 22 | 40.00 |
| IRS990/Form990PartVIISectionAGrp/AverageHoursPerWeekRt | 23 | 40.00 |
| IRS990/Form990PartVIISectionAGrp/AverageHoursPerWeekRt | 24 | 40.00 |
| IRS990/Form990PartVIISectionAGrp/AverageHoursPerWeekRt | 25 | 40.00 |
| IRS990/Form990PartVIISectionAGrp/AverageHoursPerWeekRt | 26 | 40.00 |
| IRS990/Form990PartVIISectionAGrp/AverageHoursPerWeekRt | 27 | 40.00 |
| IRS990/Form990PartVIISectionAGrp/HighestCompensatedEmployeeInd | 0 | X |
| IRS990/Form990PartVIISectionAGrp/HighestCompensatedEmployeeInd | 1 | X |
| IRS990/Form990PartVIISectionAGrp/HighestCompensatedEmployeeInd | 2 | X |
| IRS990/Form990PartVIISectionAGrp/HighestCompensatedEmployeeInd | 3 | X |
| IRS990/Form990PartVIISectionAGrp/HighestCompensatedEmployeeInd | 4 | X |
| IRS990/Form990PartVIISectionAGrp/IndividualTrusteeOrDirectorInd | 0 | X |
| IRS990/Form990PartVIISectionAGrp/IndividualTrusteeOrDirectorInd | 1 | X |
| IRS990/Form990PartVIISectionAGrp/IndividualTrusteeOrDirectorInd | 2 | X |
| IRS990/Form990PartVIISectionAGrp/IndividualTrusteeOrDirectorInd | 3 | X |
| IRS990/Form990PartVIISectionAGrp/IndividualTrusteeOrDirectorInd | 4 | X |
| IRS990/Form990PartVIISectionAGrp/IndividualTrusteeOrDirectorInd | 5 | X |
| IRS990/Form990PartVIISectionAGrp/IndividualTrusteeOrDirectorInd | 6 | X |
| IRS990/Form990PartVIISectionAGrp/IndividualTrusteeOrDirectorInd | 7 | X |
| IRS990/Form990PartVIISectionAGrp/IndividualTrusteeOrDirectorInd | 8 | X |
| IRS990/Form990PartVIISectionAGrp/IndividualTrusteeOrDirectorInd | 9 | X |
| IRS990/Form990PartVIISectionAGrp/IndividualTrusteeOrDirectorInd | 10 | X |
| IRS990/Form990PartVIISectionAGrp/IndividualTrusteeOrDirectorInd | 11 | X |
| IRS990/Form990PartVIISectionAGrp/IndividualTrusteeOrDirectorInd | 12 | X |
| IRS990/Form990PartVIISectionAGrp/IndividualTrusteeOrDirectorInd | 13 | X |
| IRS990/Form990PartVIISectionAGrp/IndividualTrusteeOrDirectorInd | 14 | X |
| IRS990/Form990PartVIISectionAGrp/IndividualTrusteeOrDirectorInd | 15 | X |
| IRS990/Form990PartVIISectionAGrp/IndividualTrusteeOrDirectorInd | 16 | X |
| IRS990/Form990PartVIISectionAGrp/IndividualTrusteeOrDirectorInd | 17 | X |
| IRS990/Form990PartVIISectionAGrp/IndividualTrusteeOrDirectorInd | 18 | X |
| IRS990/Form990PartVIISectionAGrp/IndividualTrusteeOrDirectorInd | 19 | X |
| IRS990/Form990PartVIISectionAGrp/IndividualTrusteeOrDirectorInd | 20 | X |
| IRS990/Form990PartVIISectionAGrp/IndividualTrusteeOrDirectorInd | 21 | X |
| IRS990/Form990PartVIISectionAGrp/KeyEmployeeInd | 0 | X |
| IRS990/Form990PartVIISectionAGrp/OfficerInd | 0 | X |
| IRS990/Form990PartVIISectionAGrp/OfficerInd | 1 | X |
| IRS990/Form990PartVIISectionAGrp/OfficerInd | 2 | X |
| IRS990/Form990PartVIISectionAGrp/OfficerInd | 3 | X |
| IRS990/Form990PartVIISectionAGrp/OfficerInd | 4 | X |
| IRS990/Form990PartVIISectionAGrp/OfficerInd | 5 | X |
| IRS990/Form990PartVIISectionAGrp/OtherCompensationAmt | 0 | 0 |
| IRS990/Form990PartVIISectionAGrp/OtherCompensationAmt | 1 | 0 |
| IRS990/Form990PartVIISectionAGrp/OtherCompensationAmt | 2 | 0 |
| IRS990/Form990PartVIISectionAGrp/OtherCompensationAmt | 3 | 0 |
| IRS990/Form990PartVIISectionAGrp/OtherCompensationAmt | 4 | 0 |
| IRS990/Form990PartVIISectionAGrp/OtherCompensationAmt | 5 | 0 |
| IRS990/Form990PartVIISectionAGrp/OtherCompensationAmt | 6 | 0 |
| IRS990/Form990PartVIISectionAGrp/OtherCompensationAmt | 7 | 15083 |
| IRS990/Form990PartVIISectionAGrp/OtherCompensationAmt | 8 | 0 |
| IRS990/Form990PartVIISectionAGrp/OtherCompensationAmt | 9 | 0 |
| IRS990/Form990PartVIISectionAGrp/OtherCompensationAmt | 10 | 0 |
| IRS990/Form990PartVIISectionAGrp/OtherCompensationAmt | 11 | 0 |
| IRS990/Form990PartVIISectionAGrp/OtherCompensationAmt | 12 | 0 |
| IRS990/Form990PartVIISectionAGrp/OtherCompensationAmt | 13 | 0 |
| IRS990/Form990PartVIISectionAGrp/OtherCompensationAmt | 14 | 0 |
| IRS990/Form990PartVIISectionAGrp/OtherCompensationAmt | 15 | 0 |
| IRS990/Form990PartVIISectionAGrp/OtherCompensationAmt | 16 | 0 |
| IRS990/Form990PartVIISectionAGrp/OtherCompensationAmt | 17 | 0 |
| IRS990/Form990PartVIISectionAGrp/OtherCompensationAmt | 18 | 0 |
| IRS990/Form990PartVIISectionAGrp/OtherCompensationAmt | 19 | 0 |
| IRS990/Form990PartVIISectionAGrp/OtherCompensationAmt | 20 | 0 |
| IRS990/Form990PartVIISectionAGrp/OtherCompensationAmt | 21 | 264868 |
| IRS990/Form990PartVIISectionAGrp/OtherCompensationAmt | 22 | 31492 |
| IRS990/Form990PartVIISectionAGrp/OtherCompensationAmt | 23 | 17967 |
| IRS990/Form990PartVIISectionAGrp/OtherCompensationAmt | 24 | 17997 |
| IRS990/Form990PartVIISectionAGrp/OtherCompensationAmt | 25 | 17397 |
| IRS990/Form990PartVIISectionAGrp/OtherCompensationAmt | 26 | 12909 |
| IRS990/Form990PartVIISectionAGrp/OtherCompensationAmt | 27 | 17097 |
| IRS990/Form990PartVIISectionAGrp/PersonNm | 0 | ELLIOT GORDON |
| IRS990/Form990PartVIISectionAGrp/PersonNm | 1 | BENNETT ROSENTHAL |
| IRS990/Form990PartVIISectionAGrp/PersonNm | 2 | BRYAN EZRALOW |
| IRS990/Form990PartVIISectionAGrp/PersonNm | 3 | ALLISON MIRKIN |
| IRS990/Form990PartVIISectionAGrp/PersonNm | 4 | TONY RUBIN |
| IRS990/Form990PartVIISectionAGrp/PersonNm | 5 | MARY BRUSSELL |
| IRS990/Form990PartVIISectionAGrp/PersonNm | 6 | PATRICIA DUNCAN |
| IRS990/Form990PartVIISectionAGrp/PersonNm | 7 | BRUCE ESKOVITZ |
| IRS990/Form990PartVIISectionAGrp/PersonNm | 8 | TED FIKRE |
| IRS990/Form990PartVIISectionAGrp/PersonNm | 9 | NANCY GLASER |
| IRS990/Form990PartVIISectionAGrp/PersonNm | 10 | JANE GUTMAN |
| IRS990/Form990PartVIISectionAGrp/PersonNm | 11 | MICHAEL HACKMAN |
| IRS990/Form990PartVIISectionAGrp/PersonNm | 12 | EMILY KOVNER MOSS |
| IRS990/Form990PartVIISectionAGrp/PersonNm | 13 | NORA MALONE |
| IRS990/Form990PartVIISectionAGrp/PersonNm | 14 | BILL MCMORROW |
| IRS990/Form990PartVIISectionAGrp/PersonNm | 15 | MICHAEL PARKS |
| IRS990/Form990PartVIISectionAGrp/PersonNm | 16 | RANDYE SORE |
| IRS990/Form990PartVIISectionAGrp/PersonNm | 17 | MARVIN SUOMI |
| IRS990/Form990PartVIISectionAGrp/PersonNm | 18 | KAROL WATSON |
| IRS990/Form990PartVIISectionAGrp/PersonNm | 19 | PERRIE WEINER |
| IRS990/Form990PartVIISectionAGrp/PersonNm | 20 | NEIL WERTLIEB |
| IRS990/Form990PartVIISectionAGrp/PersonNm | 21 | THOMAS GILDER |
| IRS990/Form990PartVIISectionAGrp/PersonNm | 22 | STEVEN W KIERMAN |
| IRS990/Form990PartVIISectionAGrp/PersonNm | 23 | MARGARET PROCTER |
| IRS990/Form990PartVIISectionAGrp/PersonNm | 24 | ERIC MANDEL |
| IRS990/Form990PartVIISectionAGrp/PersonNm | 25 | RAYMOND FRIEND |
| IRS990/Form990PartVIISectionAGrp/PersonNm | 26 | JAMES BOLOGNA |
| IRS990/Form990PartVIISectionAGrp/PersonNm | 27 | SHARON PEARLINE |
| IRS990/Form990PartVIISectionAGrp/ReportableCompFromOrgAmt | 0 | 0 |
| IRS990/Form990PartVIISectionAGrp/ReportableCompFromOrgAmt | 1 | 0 |
| IRS990/Form990PartVIISectionAGrp/ReportableCompFromOrgAmt | 2 | 0 |
| IRS990/Form990PartVIISectionAGrp/ReportableCompFromOrgAmt | 3 | 0 |
| IRS990/Form990PartVIISectionAGrp/ReportableCompFromOrgAmt | 4 | 0 |
| IRS990/Form990PartVIISectionAGrp/ReportableCompFromOrgAmt | 5 | 0 |
| IRS990/Form990PartVIISectionAGrp/ReportableCompFromOrgAmt | 6 | 0 |
| IRS990/Form990PartVIISectionAGrp/ReportableCompFromOrgAmt | 7 | 115053 |
| IRS990/Form990PartVIISectionAGrp/ReportableCompFromOrgAmt | 8 | 0 |
| IRS990/Form990PartVIISectionAGrp/ReportableCompFromOrgAmt | 9 | 0 |
| IRS990/Form990PartVIISectionAGrp/ReportableCompFromOrgAmt | 10 | 0 |
| IRS990/Form990PartVIISectionAGrp/ReportableCompFromOrgAmt | 11 | 0 |
| IRS990/Form990PartVIISectionAGrp/ReportableCompFromOrgAmt | 12 | 0 |
| IRS990/Form990PartVIISectionAGrp/ReportableCompFromOrgAmt | 13 | 0 |
| IRS990/Form990PartVIISectionAGrp/ReportableCompFromOrgAmt | 14 | 0 |
| IRS990/Form990PartVIISectionAGrp/ReportableCompFromOrgAmt | 15 | 0 |
| IRS990/Form990PartVIISectionAGrp/ReportableCompFromOrgAmt | 16 | 0 |
| IRS990/Form990PartVIISectionAGrp/ReportableCompFromOrgAmt | 17 | 0 |
| IRS990/Form990PartVIISectionAGrp/ReportableCompFromOrgAmt | 18 | 0 |
| IRS990/Form990PartVIISectionAGrp/ReportableCompFromOrgAmt | 19 | 0 |
| IRS990/Form990PartVIISectionAGrp/ReportableCompFromOrgAmt | 20 | 0 |
| IRS990/Form990PartVIISectionAGrp/ReportableCompFromOrgAmt | 21 | 358015 |
| IRS990/Form990PartVIISectionAGrp/ReportableCompFromOrgAmt | 22 | 248658 |
| IRS990/Form990PartVIISectionAGrp/ReportableCompFromOrgAmt | 23 | 158775 |
| IRS990/Form990PartVIISectionAGrp/ReportableCompFromOrgAmt | 24 | 151171 |
| IRS990/Form990PartVIISectionAGrp/ReportableCompFromOrgAmt | 25 | 156169 |
| IRS990/Form990PartVIISectionAGrp/ReportableCompFromOrgAmt | 26 | 136602 |
| IRS990/Form990PartVIISectionAGrp/ReportableCompFromOrgAmt | 27 | 138180 |
| IRS990/Form990PartVIISectionAGrp/ReportableCompFromRltdOrgAmt | 0 | 0 |
| IRS990/Form990PartVIISectionAGrp/ReportableCompFromRltdOrgAmt | 1 | 0 |
| IRS990/Form990PartVIISectionAGrp/ReportableCompFromRltdOrgAmt | 2 | 0 |
| IRS990/Form990PartVIISectionAGrp/ReportableCompFromRltdOrgAmt | 3 | 0 |
| IRS990/Form990PartVIISectionAGrp/ReportableCompFromRltdOrgAmt | 4 | 0 |
| IRS990/Form990PartVIISectionAGrp/ReportableCompFromRltdOrgAmt | 5 | 0 |
| IRS990/Form990PartVIISectionAGrp/ReportableCompFromRltdOrgAmt | 6 | 0 |
| IRS990/Form990PartVIISectionAGrp/ReportableCompFromRltdOrgAmt | 7 | 0 |
| IRS990/Form990PartVIISectionAGrp/ReportableCompFromRltdOrgAmt | 8 | 0 |
| IRS990/Form990PartVIISectionAGrp/ReportableCompFromRltdOrgAmt | 9 | 0 |
| IRS990/Form990PartVIISectionAGrp/ReportableCompFromRltdOrgAmt | 10 | 0 |
| IRS990/Form990PartVIISectionAGrp/ReportableCompFromRltdOrgAmt | 11 | 0 |
| IRS990/Form990PartVIISectionAGrp/ReportableCompFromRltdOrgAmt | 12 | 0 |
| IRS990/Form990PartVIISectionAGrp/ReportableCompFromRltdOrgAmt | 13 | 0 |
| IRS990/Form990PartVIISectionAGrp/ReportableCompFromRltdOrgAmt | 14 | 0 |
| IRS990/Form990PartVIISectionAGrp/ReportableCompFromRltdOrgAmt | 15 | 0 |
| IRS990/Form990PartVIISectionAGrp/ReportableCompFromRltdOrgAmt | 16 | 0 |
| IRS990/Form990PartVIISectionAGrp/ReportableCompFromRltdOrgAmt | 17 | 0 |
| IRS990/Form990PartVIISectionAGrp/ReportableCompFromRltdOrgAmt | 18 | 0 |
| IRS990/Form990PartVIISectionAGrp/ReportableCompFromRltdOrgAmt | 19 | 0 |
| IRS990/Form990PartVIISectionAGrp/ReportableCompFromRltdOrgAmt | 20 | 0 |
| IRS990/Form990PartVIISectionAGrp/ReportableCompFromRltdOrgAmt | 21 | 0 |
| IRS990/Form990PartVIISectionAGrp/ReportableCompFromRltdOrgAmt | 22 | 0 |
| IRS990/Form990PartVIISectionAGrp/ReportableCompFromRltdOrgAmt | 23 | 0 |
| IRS990/Form990PartVIISectionAGrp/ReportableCompFromRltdOrgAmt | 24 | 0 |
| IRS990/Form990PartVIISectionAGrp/ReportableCompFromRltdOrgAmt | 25 | 0 |
| IRS990/Form990PartVIISectionAGrp/ReportableCompFromRltdOrgAmt | 26 | 0 |
| IRS990/Form990PartVIISectionAGrp/ReportableCompFromRltdOrgAmt | 27 | 0 |
| IRS990/Form990PartVIISectionAGrp/TitleTxt | 0 | PRESIDENT |
| IRS990/Form990PartVIISectionAGrp/TitleTxt | 1 | CFO/TREASURER |
| IRS990/Form990PartVIISectionAGrp/TitleTxt | 2 | VICE CHAIR |
| IRS990/Form990PartVIISectionAGrp/TitleTxt | 3 | VICE CHAIR |
| IRS990/Form990PartVIISectionAGrp/TitleTxt | 4 | VICE CHAIR |
| IRS990/Form990PartVIISectionAGrp/TitleTxt | 5 | PARENT GUILD REPRESENTATIVE |
| IRS990/Form990PartVIISectionAGrp/TitleTxt | 6 | BOARD MEMBER |
| IRS990/Form990PartVIISectionAGrp/TitleTxt | 7 | BOARD MEMBER / TEACHER |
| IRS990/Form990PartVIISectionAGrp/TitleTxt | 8 | BOARD MEMBER |
| IRS990/Form990PartVIISectionAGrp/TitleTxt | 9 | BOARD MEMBER |
| IRS990/Form990PartVIISectionAGrp/TitleTxt | 10 | BOARD MEMBER |
| IRS990/Form990PartVIISectionAGrp/TitleTxt | 11 | BOARD MEMBER |
| IRS990/Form990PartVIISectionAGrp/TitleTxt | 12 | BOARD MEMBER |
| IRS990/Form990PartVIISectionAGrp/TitleTxt | 13 | BOARD MEMBER |
| IRS990/Form990PartVIISectionAGrp/TitleTxt | 14 | BOARD MEMBER |
| IRS990/Form990PartVIISectionAGrp/TitleTxt | 15 | BOARD MEMBER |
| IRS990/Form990PartVIISectionAGrp/TitleTxt | 16 | BOARD MEMBER |
| IRS990/Form990PartVIISectionAGrp/TitleTxt | 17 | BOARD MEMBER |
| IRS990/Form990PartVIISectionAGrp/TitleTxt | 18 | BOARD MEMBER |
| IRS990/Form990PartVIISectionAGrp/TitleTxt | 19 | BOARD MEMBER |
| IRS990/Form990PartVIISectionAGrp/TitleTxt | 20 | BOARD MEMBER |
| IRS990/Form990PartVIISectionAGrp/TitleTxt | 21 | HEAD OF SCHOOL/SECRETARY |
| IRS990/Form990PartVIISectionAGrp/TitleTxt | 22 | DIRECTOR OF FINANCE |
| IRS990/Form990PartVIISectionAGrp/TitleTxt | 23 | DIRECTOR OF THE UPPER SCHOOL |
| IRS990/Form990PartVIISectionAGrp/TitleTxt | 24 | DIRECTOR OF THE LOWER SCHOOL |
| IRS990/Form990PartVIISectionAGrp/TitleTxt | 25 | DEAN OF FACULTY |
| IRS990/Form990PartVIISectionAGrp/TitleTxt | 26 | MANAGER OF INFRASTUCTURE |
| IRS990/Form990PartVIISectionAGrp/TitleTxt | 27 | DIRECTOR OF ADMISSIONS |
| IRS990/Form990ProvidedToGvrnBodyInd | 0 | 0 |
| IRS990/FormationYr | 0 | 1971 |
| IRS990/FormerOfcrEmployeesListedInd | 0 | 0 |
| IRS990/FSAuditedBasisGrp/SeparateBasisFinclStmtInd | 0 | X |
| IRS990/FSAuditedInd | 0 | 1 |
| IRS990/FundraisingActivitiesInd | 0 | 1 |
| IRS990/FundraisingDirectExpensesAmt | 0 | 93425 |
| IRS990/FundraisingGrossIncomeAmt | 0 | 335549 |
| IRS990/GainOrLossGrp/SecuritiesAmt | 0 | -333971 |
| IRS990/GamingActivitiesInd | 0 | 0 |
| IRS990/GoverningBodyVotingMembersCnt | 0 | 22 |
| IRS990/GrantAmt | 0 | 2179557 |
| IRS990/GrantsToDomesticIndividualsGrp/ProgramServicesAmt | 0 | 2179557 |
| IRS990/GrantsToDomesticIndividualsGrp/TotalAmt | 0 | 2179557 |
| IRS990/GrantsToIndividualsInd | 0 | 1 |
| IRS990/GrantsToOrganizationsInd | 0 | 0 |
| IRS990/GrantToRelatedPersonInd | 0 | 0 |
| IRS990/GrossAmountSalesAssetsGrp/SecuritiesAmt | 0 | 771617 |
| IRS990/GrossReceiptsAmt | 0 | 29179829 |
| IRS990/GrossRentsGrp/RealAmt | 0 | 289558 |
| IRS990/GroupReturnForAffiliatesInd | 0 | 0 |
| IRS990/IncludeFIN48FootnoteInd | 0 | 1 |
| IRS990/IndependentAuditFinclStmtInd | 0 | 1 |
| IRS990/IndependentVotingMemberCnt | 0 | 20 |
| IRS990/IndivRcvdGreaterThan100KCnt | 0 | 34 |
| IRS990/IndoorTanningServicesInd | 0 | 0 |
| IRS990/InfoInScheduleOPartIIIInd | 0 | X |
| IRS990/InfoInScheduleOPartVIInd | 0 | X |
| IRS990/InformationTechnologyGrp/ManagementAndGeneralAmt | 0 | 150 |
| IRS990/InformationTechnologyGrp/ProgramServicesAmt | 0 | 268010 |
| IRS990/InformationTechnologyGrp/TotalAmt | 0 | 268160 |
| IRS990/InsuranceGrp/FundraisingAmt | 0 | 11966 |
| IRS990/InsuranceGrp/ManagementAndGeneralAmt | 0 | 52911 |
| IRS990/InsuranceGrp/ProgramServicesAmt | 0 | 215788 |
| IRS990/InsuranceGrp/TotalAmt | 0 | 280665 |
| IRS990/InterestGrp/FundraisingAmt | 0 | 30057 |
| IRS990/InterestGrp/ManagementAndGeneralAmt | 0 | 142772 |
| IRS990/InterestGrp/ProgramServicesAmt | 0 | 593611 |
| IRS990/InterestGrp/TotalAmt | 0 | 766440 |
| IRS990/InvestmentIncomeGrp/ExclusionAmt | 0 | 189150 |
| IRS990/InvestmentIncomeGrp/TotalRevenueColumnAmt | 0 | 189150 |
| IRS990/InvestmentInJointVentureInd | 0 | 0 |
| IRS990/InvestmentsOtherSecuritiesGrp/BOYAmt | 0 | 3490804 |
| IRS990/InvestmentsOtherSecuritiesGrp/EOYAmt | 0 | 3743108 |
| IRS990/InvestmentsPubTradedSecGrp/BOYAmt | 0 | 8421525 |
| IRS990/InvestmentsPubTradedSecGrp/EOYAmt | 0 | 12556682 |
| IRS990/InvestTaxExemptBondsInd | 0 | 0 |
| IRS990/IRPDocumentCnt | 0 | 64 |
| IRS990/IRPDocumentW2GCnt | 0 | 0 |
| IRS990/LandBldgEquipAccumDeprecAmt | 0 | 18386939 |
| IRS990/LandBldgEquipBasisNetGrp/BOYAmt | 0 | 34325112 |
| IRS990/LandBldgEquipBasisNetGrp/EOYAmt | 0 | 37251090 |
| IRS990/LandBldgEquipCostOrOtherBssAmt | 0 | 55638029 |
| IRS990/LegalDomicileStateCd | 0 | CA |
| IRS990/LessCostOthBasisSalesExpnssGrp/SecuritiesAmt | 0 | 1105588 |
| IRS990/LessRentalExpensesGrp/RealAmt | 0 | 273021 |
| IRS990/LoanOutstandingInd | 0 | 0 |
| IRS990/LobbyingActivitiesInd | 0 | 0 |
| IRS990/LocalChaptersInd | 0 | 0 |
| IRS990/MaterialDiversionOrMisuseInd | 0 | 0 |
| IRS990/MembersOrStockholdersInd | 0 | 0 |
| IRS990/MethodOfAccountingAccrualInd | 0 | X |
| IRS990/MinutesOfCommitteesInd | 0 | 1 |
| IRS990/MinutesOfGoverningBodyInd | 0 | 1 |
| IRS990/MiscellaneousRevenueGrp/ExclusionAmt | 0 | 379753 |
| IRS990/MiscellaneousRevenueGrp/TotalRevenueColumnAmt | 0 | 379753 |
| IRS990/MissionDesc | 0 | WINDWARD SCHOOL IS A DYNAMIC COLLEGE-PREPARATORY SCHOOL THAT CHALLENGES EACH STUDENT TO ACHIEVE EXCELLENCE IN A NURTURING, INCLUSIVE COMMUNITY. WINDWARD TEACHERS, PARENTS, AND ADMINISTRATORS WORK TOGETHER TO INSPIRE OUR STUDENTS TO BE RESPONSIBLE, CARING, WELL INFORMED, ETHICAL, PREPARED, AND WELL BALANCED YOUNG ADULTS. |
| IRS990/MoreThan5000KToIndividualsInd | 0 | 0 |
| IRS990/MoreThan5000KToOrgInd | 0 | 0 |
| IRS990/NetAssetsOrFundBalancesBOYAmt | 0 | 29885316 |
| IRS990/NetAssetsOrFundBalancesEOYAmt | 0 | 31368074 |
| IRS990/NetGainOrLossInvestmentsGrp/ExclusionAmt | 0 | -333971 |
| IRS990/NetGainOrLossInvestmentsGrp/TotalRevenueColumnAmt | 0 | -333971 |
| IRS990/NetIncmFromFundraisingEvtGrp/ExclusionAmt | 0 | 242124 |
| IRS990/NetIncmFromFundraisingEvtGrp/TotalRevenueColumnAmt | 0 | 242124 |
| IRS990/NetRentalIncomeOrLossGrp/ExclusionAmt | 0 | 16537 |
| IRS990/NetRentalIncomeOrLossGrp/TotalRevenueColumnAmt | 0 | 16537 |
| IRS990/NetUnrelatedBusTxblIncmAmt | 0 | 0 |
| IRS990/NetUnrlzdGainsLossesInvstAmt | 0 | 283391 |
| IRS990/NoncashContributionsAmt | 0 | 678049 |
| IRS990/NondeductibleContributionsInd | 0 | 0 |
| IRS990/OccupancyGrp/FundraisingAmt | 0 | 66987 |
| IRS990/OccupancyGrp/ManagementAndGeneralAmt | 0 | 296205 |
| IRS990/OccupancyGrp/ProgramServicesAmt | 0 | 1208015 |
| IRS990/OccupancyGrp/TotalAmt | 0 | 1571207 |
| IRS990/OfficeExpensesGrp/FundraisingAmt | 0 | 12704 |
| IRS990/OfficeExpensesGrp/ManagementAndGeneralAmt | 0 | 73653 |
| IRS990/OfficeExpensesGrp/ProgramServicesAmt | 0 | 214511 |
| IRS990/OfficeExpensesGrp/TotalAmt | 0 | 300868 |
| IRS990/OfficerMailingAddressInd | 0 | 0 |
| IRS990/OnBehalfOfIssuerInd | 0 | 0 |
| IRS990/OperateHospitalInd | 0 | 0 |
| IRS990/Organization501c3Ind | 0 | X |
| IRS990/OrganizationFollowsSFAS117Ind | 0 | X |
| IRS990/OtherAssetsTotalGrp/BOYAmt | 0 | 223148 |
| IRS990/OtherAssetsTotalGrp/EOYAmt | 0 | 192159 |
| IRS990/OtherChangesInNetAssetsAmt | 0 | 0 |
| IRS990/OtherEmployeeBenefitsGrp/FundraisingAmt | 0 | 119950 |