Summary of Significant Accounting Policies - Additional Information (Detail) shares in Thousands		1 Months Ended		6 Months Ended	9 Months Ended
	Jul. 01, 2018 USD ($)	Jun. 30, 2018 USD ($) Employee shares	May 31, 2017 USD ($) Employee shares	Jun. 30, 2018 USD ($)	Sep. 30, 2018 USD ($) Project Agency	Sep. 30, 2017 USD ($)	Dec. 31, 2017 USD ($)
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
Period of LIBOR interest rate					30 days
Reduction in revenue due to scholarships offered to students				$ 101,176,000		$ 135,630,000
Royalty amortization period					20 years
Remaining prepaid royalty assets impaired	$ 3,037,000
Number of stages of software development projects | Project					3
Cumulative effect from the adoption of accounting pronouncements, net of taxes					$ 1,174,000
Deferred revenue							$ 46,895,000
Computer Software, Intangible Asset [Member]
Summary Of Significant Accounting Policies [Line Items]
Estimated useful life					3 years
Grand Canyon University [Member]
Summary Of Significant Accounting Policies [Line Items]
Remaining prepaid royalty assets impaired					$ 3,037,000
Number of former employees hired | Employee		100	100
Share-based compensation expense for restricted stock awards					$ 7,880,000
Grand Canyon University [Member] | Restricted Stock Grants [Member]
Summary Of Significant Accounting Policies [Line Items]
Shares issued under plan | shares		82	82
Share-based compensation expense for restricted stock awards		$ 7,880,000	$ 7,880,000
Grand Canyon University [Member] | Master Services Agreement [Member]
Summary Of Significant Accounting Policies [Line Items]
Percentage of tuition and fee revenue used for closing of purchase agreement					60.00%
Initial maturity period of agreement					15 years
Early termination period of agreement					7 years
Refund or return rights under agreement					$ 0
Interest Rate Corridor [Member]
Summary Of Significant Accounting Policies [Line Items]
Notional amount of derivative instrument					$ 61,667,000
Description of interest rate risk hedge at several thresholds					The Company 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 Company pays 1.5%. If 30 Day LIBOR exceeds 3.0%, the Company pays actual 30 Day LIBOR less 1.5%.
Interest Rate Corridor [Member] | LIBOR [Member]
Summary Of Significant Accounting Policies [Line Items]
Maximum percentage of variable interest rates based on LIBOR					1.50%
Percentage of amount paid by Company					1.50%
Percentage deducted from LIBOR for actual payment					1.50%
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					$ 330,000	$ 169,000
Other Assets [Member]
Summary Of Significant Accounting Policies [Line Items]
Fair values of interest rate corridor instrument					$ 801,000		$ 509,000
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
Number of major rating agencies reporting credit ratings | Agency					1
Minimum [Member] | Interest Rate Corridor [Member] | LIBOR [Member]
Summary Of Significant Accounting Policies [Line Items]
Percentage of LIBOR					1.50%
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
Maximum [Member] | Interest Rate Corridor [Member] | LIBOR [Member]
Summary Of Significant Accounting Policies [Line Items]
Percentage of LIBOR					3.00%
Revenue from Contracts with Customers [Member] | Difference between Revenue Guidance in Effect before and after Topic 606 [Member]
Summary Of Significant Accounting Policies [Line Items]
Direct and incremental capitalized costs					$ 9,015,000
Deferred revenue					$ 7,451,000