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Property and Equipment - Additional Information (Detail) - USD ($) $ in Thousands | 12 Months Ended
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Dec. 31, 2017 | Dec. 31, 2016 | Dec. 31, 2015
Property, Plant and Equipment [Abstract] |  |  |
Depreciation and amortization expense including assets under capital lease | $ 53,607 | $ 44,829 | $ 34,821

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- Definition Depreciation and amortization including assets under capital lease. + References No definition available. + Details
Name: | lope_DepreciationAndAmortizationIncludingAssetsUnderCapitalLease
Namespace Prefix: | lope_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

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- References No definition available. + Details
Name: | us-gaap_PropertyPlantAndEquipmentAbstract
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration