Significant Accounting Policies - Tuition Receivable (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Schedule of tuition receivable and allowance for doubtful accounts
Tuition receivable	$ 100,060	$ 99,942
Allowance for credit losses	(48,783)	(49,773)
Tuition receivable, net	51,277	50,169
Tuition receivable, noncurrent	2,466	3,585
Other assets
Schedule of tuition receivable and allowance for doubtful accounts
Tuition receivable, noncurrent	$ 2,500	$ 3,600