Summary of Significant Accounting Policies - Additional Information (Details) $ in Thousands		3 Months Ended		9 Months Ended	12 Months Ended
	Jul. 01, 2018 USD ($)	Mar. 31, 2021 USD ($) segment item	Mar. 31, 2020 USD ($)	Sep. 30, 2020 USD ($)	Dec. 31, 2019 USD ($)	Dec. 31, 2020 USD ($)
Summary Of Significant Accounting Policies
Other assets		$ 2,133				$ 1,844
Number of operating segments | segment		1
Number of reporting units | segment		1
Unbilled revenue		$ 10,132				294
Amounts written off		0
Allowance for doubtful accounts		0
Lease liabilities		62,583
Secured Note receivable, carrying value		964,912				964,912
Secured Note receivable, fair value		$ 1,045,591				1,049,458
Number of university partners | item		26
Allowance for credit losses		$ 5,000	$ 5,000		$ 5,000	5,000
Stockholders equity		1,588,678	1,448,008		1,443,433	1,574,329
Income tax expense		$ 19,985	$ 22,791
Revenue Benchmark | Customer Concentration Risk
Summary Of Significant Accounting Policies
Concentration risk percentage		87.40%	87.90%
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		$ 1,166				$ 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%
Term of additional lending to GCU for approved capital expenditures	3 years
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
Stockholders equity			(3,832)		(3,832)
Income tax expense			$ 1,168		$ 1,168