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Summary of Significant Accounting Policies - Additional Information (Details) $ in Thousands		3 Months Ended
	Jul. 01, 2018	Mar. 31, 2019 USD ($)	Mar. 31, 2018 USD ($)	Mar. 31, 2019 Institution	Mar. 31, 2019 USD ($)	Jan. 22, 2019 USD ($)	Jan. 01, 2019 USD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)
Summary Of Significant Accounting Policies [Line Items]
Costs capitalized to obtain or fulfill contracts with customers					$ 0
Unbilled revenue					1,556
Reduction in revenue due to scholarships offered to students			$ 60,241
Other assets					2,020			$ 478
Amounts written off		$ 0	3,722
Allowance for doubtful accounts			7,182		0				$ 5,907
Number of university partners		18		18
Cumulative effect from the adoption of accounting pronouncements, net of taxes			(1,174)
Right-of-use assets					13,186		$ 498
Lease liabilities					13,266		$ 498
Right-of-use assets						$ 13,069
Lease liability						$ 13,069
Election of hindsight practical expedient		true
Election of package of practical expedients		true
Cumulative effect from the adoption of accounting pronouncements, net of taxes			1,174
Computer Software, Intangible Asset [Member]
Summary Of Significant Accounting Policies [Line Items]
Estimated Average Useful Life		3 years
Capitalized Content Development
Summary Of Significant Accounting Policies [Line Items]
Other assets					1,222
Estimated Average Useful Life		4 years
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%
Interest Rate Corridor [Member]
Summary Of Significant Accounting Policies [Line Items]
Notional amount of derivative instrument					58,333
Interest Rate Corridor [Member] \| 30 Day LIBOR equal to 1.5% through 3.0%
Summary Of Significant Accounting Policies [Line Items]
Interest rate spread on 30 Day LIBOR		1.50%
Interest Rate Corridor [Member] \| 30 Day LIBOR exceeds 3.0%
Summary Of Significant Accounting Policies [Line Items]
Interest rate spread on 30 Day LIBOR		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		$ 142	$ 231
Other Assets [Member]
Summary Of Significant Accounting Policies [Line Items]
Fair values of interest rate corridor instrument					$ 423			$ 600
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
Initial contract terms		7 years
Minimum [Member] \| Interest Rate Corridor [Member] \| 30 Day LIBOR equal to 1.5% through 3.0%
Summary Of Significant Accounting Policies [Line Items]
30 Day LIBOR index rate		1.50%
Minimum [Member] \| Interest Rate Corridor [Member] \| 30 Day LIBOR exceeds 3.0%
Summary Of Significant Accounting Policies [Line Items]
30 Day LIBOR index rate		3.00%
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
Initial contract terms		15 years
Maximum [Member] \| Interest Rate Corridor [Member] \| LIBOR [Member]
Summary Of Significant Accounting Policies [Line Items]
30 Day LIBOR index rate		1.50%
Maximum [Member] \| Interest Rate Corridor [Member] \| 30 Day LIBOR equal to 1.5% through 3.0%
Summary Of Significant Accounting Policies [Line Items]
30 Day LIBOR index rate		3.00%