Stockholders' Equity - Stock-based Compensation Expense (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Stock-based compensation expense included in the unaudited condensed consolidated statements of operations
Total stock-based compensation expense	$ 10,440	$ 15,967	$ 35,986	$ 62,740
Curriculum and teaching
Stock-based compensation expense included in the unaudited condensed consolidated statements of operations
Total stock-based compensation expense	37	59	128	155
Servicing and support
Stock-based compensation expense included in the unaudited condensed consolidated statements of operations
Total stock-based compensation expense	2,257	3,061	7,773	11,741
Technology and content development
Stock-based compensation expense included in the unaudited condensed consolidated statements of operations
Total stock-based compensation expense	737	1,288	4,354	7,785
Marketing and sales
Stock-based compensation expense included in the unaudited condensed consolidated statements of operations
Total stock-based compensation expense	1,436	1,013	3,959	4,861
General and administrative
Stock-based compensation expense included in the unaudited condensed consolidated statements of operations
Total stock-based compensation expense	$ 5,973	$ 10,546	$ 19,772	$ 38,198