Equity Awards - Stock-based compensation (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Schedule of stock-based compensation expense
Stock-based compensation expense included in operating expense	$ 5,529	$ 4,168	$ 10,597	$ 8,068
Tax benefit	1,456	1,131	2,790	2,131
Stock-based compensation expense, net of tax	4,073	3,037	7,807	5,937
Instructional and support costs
Schedule of stock-based compensation expense
Stock-based compensation expense included in operating expense	1,781	1,281	3,388	2,506
General and administration
Schedule of stock-based compensation expense
Stock-based compensation expense included in operating expense	3,748	3,368	7,209	6,043
Restructuring costs
Schedule of stock-based compensation expense
Stock-based compensation expense included in operating expense	$ 0	$ (481)	$ 0	$ (481)