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Summary of Significant Accounting Policies - Additional Information (Detail) (USD $)
 3 Months Ended 12 Months Ended
Mar. 31, 2015
Mar. 31, 2014
Dec. 31, 2013
Dec. 31, 2012
Dec. 31, 2014
Summary Of Significant Accounting Policies [Line Items]          
Average days from the date of receipt in which funds remain as restricted cash and cash equivalents 60 to 90 days        
Note receivable from a financial institution at fair market value       $ 27,000,000us-gaap_NotesReceivableFairValueDisclosure  
Interest rate on notes 11.00%us-gaap_ReceivableWithImputedInterestEffectiveYieldInterestRate        
Interest rate on loan 6.00%lope_FixedRateOfInterestOnLoans        
Default rate 5.00%lope_NotesReceivableInterestRate        
Interest income and other income on the loan 2,187,000us-gaap_InterestIncomeOther   1,459,000us-gaap_InterestIncomeOther    
Default interest amount 432,000us-gaap_DebtDefaultLongtermDebtAmount        
Late payment penalty amount 1,392,000lope_DefaultAmountOfLatePaymentPenaltyUnderDispute        
Statutory trustee's fee amount 139,000lope_StatutoryTrusteeFeeDueAmountUnderDispute        
Additional amount deposited in escrow 344,000us-gaap_EscrowDeposit        
Date of order for late penalty funds Oct. 28, 2013        
Period of LIBOR interest rate 30 days        
Effective portion of gain/loss on derivatives included as a component of other comprehensive income, net of taxes (239,000)us-gaap_OtherComprehensiveIncomeUnrealizedGainLossOnDerivativesArisingDuringPeriodNetOfTax (26,000)us-gaap_OtherComprehensiveIncomeUnrealizedGainLossOnDerivativesArisingDuringPeriodNetOfTax      
Description of area of the company's campus in Phoenix, Arizona 200+ acre campus        
Reduction in revenue due to scholarships offered to students 46,432,000lope_ReductionInRevenueDueToScholarshipsOfferedToStudents 37,719,000lope_ReductionInRevenueDueToScholarshipsOfferedToStudents      
Period for write off of inactive student accounts 150 days        
Interest Rate Corridor [Member]          
Summary Of Significant Accounting Policies [Line Items]          
Notional amount of derivative instrument 85,000,000invest_DerivativeNotionalAmount
/ us-gaap_DerivativeInstrumentRiskAxis
= lope_InterestRateCorridorMember		        
Description of interest rate risk hedge at several thresholds The University pays variable interest monthly based on the 30 Day LIBOR rates until that index reaches 1.5%. If 30 Day LIBOR is equal to 1.5% through 3.0%, the University pays 1.5%. If 30 Day LIBOR exceeds 3.0%, the University pays actual 30 Day LIBOR less 1.5%.        
Maximum percentage of variable interest rates based on LIBOR 1.50%lope_MaximumPercentageOfVariableInterestRatesBasedOnBaseInterestRate
/ us-gaap_DerivativeInstrumentRiskAxis
= lope_InterestRateCorridorMember		        
Debt instrument, description of variable rate basis LIBOR        
Percentage of amount paid by University 1.50%lope_PercentageOfAmountPaidByUniversity
/ us-gaap_DerivativeInstrumentRiskAxis
= lope_InterestRateCorridorMember		        
Minimum percentage of LIBOR 1.50%us-gaap_DerivativeLowerVariableInterestRateRange
/ us-gaap_DerivativeInstrumentRiskAxis
= lope_InterestRateCorridorMember		        
Maximum percentage of LIBOR 3.00%us-gaap_DerivativeHigherVariableInterestRateRange
/ us-gaap_DerivativeInstrumentRiskAxis
= lope_InterestRateCorridorMember		        
Percentage deducted from LIBOR for actual payment 1.50%lope_PercentageDeductedFromBaseInterestRateForActualPayment
/ us-gaap_DerivativeInstrumentRiskAxis
= lope_InterestRateCorridorMember		        
Interest expense on derivatives related to credit risk 3,000lope_InterestExpenseOnDerivativesRelatedToCreditRisk
/ us-gaap_DerivativeInstrumentRiskAxis
= lope_InterestRateCorridorMember		 3,000lope_InterestExpenseOnDerivativesRelatedToCreditRisk
/ us-gaap_DerivativeInstrumentRiskAxis
= lope_InterestRateCorridorMember		      
Cash Flow Hedging [Member]          
Summary Of Significant Accounting Policies [Line Items]          
Effective portion of gain/loss on derivatives included as a component of other comprehensive income, net of taxes (392,000)us-gaap_OtherComprehensiveIncomeUnrealizedGainLossOnDerivativesArisingDuringPeriodNetOfTax
/ us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis
= us-gaap_CashFlowHedgingMember		 (43,000)us-gaap_OtherComprehensiveIncomeUnrealizedGainLossOnDerivativesArisingDuringPeriodNetOfTax
/ us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis
= us-gaap_CashFlowHedgingMember		      
Other Assets [Member]          
Summary Of Significant Accounting Policies [Line Items]          
Fair values of interest rate corridor instrument $ 937,000us-gaap_CreditRiskDerivativeAssetsAtFairValue
/ us-gaap_BalanceSheetLocationAxis
= us-gaap_OtherAssetsMember		       $ 1,332,000us-gaap_CreditRiskDerivativeAssetsAtFairValue
/ us-gaap_BalanceSheetLocationAxis
= us-gaap_OtherAssetsMember
Minimum [Member]          
Summary Of Significant Accounting Policies [Line Items]          
Number of days from the date of receipt in which funds remain as restricted cash and cash equivalents 60 days        
Maximum [Member]          
Summary Of Significant Accounting Policies [Line Items]          
Number of days from the date of receipt in which funds remain as restricted cash and cash equivalents 90 days