Summary of Significant Accounting Policies - Additional Information (Details) $ in Thousands		3 Months Ended		9 Months Ended		12 Months Ended	39 Months Ended
	Jul. 01, 2018 USD ($)	Sep. 30, 2021 USD ($) item	Sep. 30, 2020 USD ($)	Sep. 30, 2021 USD ($) segment item	Sep. 30, 2020 USD ($)	Dec. 31, 2019 USD ($)	Sep. 30, 2021 USD ($) item	Jun. 30, 2021 USD ($)	Mar. 31, 2021 USD ($)	Dec. 31, 2020 USD ($)	Jun. 30, 2020 USD ($)	Mar. 31, 2020 USD ($)
Summary Of Significant Accounting Policies
Interest rate on Secured Note				6.00%
Other assets		$ 2,310		$ 2,310			$ 2,310			$ 1,844
Number of operating segments | segment				1
Number of reporting units | segment				1
Unbilled revenue		11,604		$ 11,604			11,604			294
Amounts written off				0
Allowance for doubtful accounts		0		0			0
Lease liabilities		60,674		60,674			60,674
Secured Note receivable, carrying value		964,912		964,912			964,912			964,912
Secured Note receivable, fair value		$ 1,037,256		$ 1,037,256			$ 1,037,256			1,049,458
Number of university partners | item		27		27			27
Allowance for credit losses		$ 5,000	$ 5,000	$ 5,000	$ 5,000		$ 5,000			5,000
Stockholders equity		1,400,776	1,520,983	1,400,776	1,520,983	$ 1,443,433	1,400,776	$ 1,542,683	$ 1,588,678	1,574,329	$ 1,489,387	$ 1,448,008
Income tax expense		12,166	13,141	$ 47,186	$ 51,278
Revenue Benchmark | Customer Concentration Risk | Grand Canyon University
Summary Of Significant Accounting Policies
Concentration risk percentage				85.00%	86.50%
Computer Software
Summary Of Significant Accounting Policies
Estimated average useful life				3 years
Capitalized Content Development
Summary Of Significant Accounting Policies
Estimated average useful life				4 years
Other assets		$ 1,209		$ 1,209			1,209			$ 1,198
Minimum
Summary Of Significant Accounting Policies
Initial contract terms of service agreements				7 years
Maximum
Summary Of Significant Accounting Policies
Initial contract terms of service agreements				15 years
Grand Canyon University
Summary Of Significant Accounting Policies
Purchase price of assets	$ 870,097
Interest rate on Secured Note	6.00%
Funding provided to GCU, net of repayments							$ 99,815
Master Services Agreement | Grand Canyon University
Summary Of Significant Accounting Policies
Percentage of tuition and fee revenue used for closing of purchase agreement	60.00%
Cumulative Effect of Adoption Adjustment | ASU 2016-13
Summary Of Significant Accounting Policies
Allowance for credit losses			5,000		$ 5,000	5,000
Stockholders equity			$ (3,832)		(3,832)	(3,832)
Income tax expense					$ 1,168	$ 1,168