Significant Accounting Policies - Tuition Receivable (Details) - USD ($) $ in Thousands	Mar. 31, 2022	Dec. 31, 2021
Accounts, Notes, Loans and Financing Receivable [Line Items]
Tuition receivable	$ 109,690	$ 100,060
Allowance for credit losses	(44,892)	(48,783)
Tuition receivable, net	64,798	51,277
Tuition receivable, noncurrent	2,062	2,466
Other Assets
Accounts, Notes, Loans and Financing Receivable [Line Items]
Tuition receivable, noncurrent	$ 2,100	$ 2,500