Equity Awards - Stock-based compensation (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022
Schedule of stock-based compensation expense
Stock-based compensation expense included in operating expense	$ 5,493	$ 5,529	$ 11,125	$ 10,597
Tax benefit	1,455	1,456	2,934	2,790
Stock-based compensation expense, net of tax	4,038	4,073	8,191	7,807
Instructional and support costs
Schedule of stock-based compensation expense
Stock-based compensation expense included in operating expense	1,665	1,781	3,531	3,388
General and administration
Schedule of stock-based compensation expense
Stock-based compensation expense included in operating expense	3,732	3,748	7,498	7,209
Restructuring costs
Schedule of stock-based compensation expense
Stock-based compensation expense included in operating expense	$ 96	$ 0	$ 96	$ 0