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Treasury Stock - Additional Information (Detail) (USD $)
Share data in Thousands, unless otherwise specified
 3 Months Ended 12 Months Ended
Mar. 31, 2015
Dec. 31, 2014
Stockholders Equity [Line Items]    
Expiration date on repurchase authorizations Sep. 30, 2015  
Common Stock [Member]    
Stockholders Equity [Line Items]    
Common stock acquired, shares 0us-gaap_TreasuryStockSharesAcquired
/ us-gaap_StatementEquityComponentsAxis
= us-gaap_CommonStockMember		 2,787us-gaap_TreasuryStockSharesAcquired
/ us-gaap_StatementEquityComponentsAxis
= us-gaap_CommonStockMember
Since Approval of Share Repurchase Plan [Member]    
Stockholders Equity [Line Items]    
Aggregate cost shares of common stock 49,135,000us-gaap_TreasuryStockValueAcquiredCostMethod
/ us-gaap_StatementEquityComponentsAxis
= lope_SinceApprovalOfShareRepurchasePlanMember		  
Remaining authorized repurchase amount 25,865,000us-gaap_StockRepurchaseProgramRemainingAuthorizedRepurchaseAmount1
/ us-gaap_StatementEquityComponentsAxis
= lope_SinceApprovalOfShareRepurchasePlanMember		  
Maximum [Member]    
Stockholders Equity [Line Items]    
Authorization amount for repurchase of common stock 75,000,000us-gaap_StockRepurchaseProgramAuthorizedAmount1
/ us-gaap_RangeAxis
= us-gaap_MaximumMember