Segment and Geographic Information - Geographical Information (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021	Dec. 31, 2021
Geographical Information
Total revenue	$ 241,464	$ 237,209	$ 494,793	$ 469,682
Assets	2,033,234		2,033,234		$ 2,109,006
Non-US
Geographical Information
Total revenue	27,200	26,300
Alternative Credential Segment accounts receivable
Geographical Information
Total revenue	98,374	$ 90,995	197,536	177,593
Assets	1,508,158		1,508,158		1,562,434
Alternative Credential Segment accounts receivable | Non-US
Geographical Information
Total revenue			55,300	$ 49,400
Assets	$ 3,500		$ 3,500		$ 3,300