Condensed Consolidated Statements of Operations and Comprehensive Loss - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Income Statement [Abstract]
Total revenue	$ 241,464	$ 237,209	$ 494,793	$ 469,682
Costs and expenses
Curriculum and teaching	32,145	34,788	65,375	67,936
Servicing and support	37,061	34,865	76,685	68,049
Technology and content development	45,616	42,509	96,673	85,433
Marketing and sales	116,350	114,644	247,332	227,881
General and administrative	41,523	46,160	91,758	92,787
Restructuring charges	16,753	1,334	17,540	1,819
Impairment charges	0	0	58,782	0
Total costs and expenses	289,448	274,300	654,145	543,905
Loss from operations	(47,984)	(37,091)	(159,352)	(74,223)
Interest income	241	352	498	714
Interest expense	(13,906)	(8,188)	(27,796)	(16,069)
Loss on debt extinguishment	0	(1,101)	0	(1,101)
Other income (expense), net	(1,367)	24,070	(2,397)	23,155
Loss before income taxes	(63,016)	(21,958)	(189,047)	(67,524)
Income tax benefit	164	127	415	129
Net loss	$ (62,852)	$ (21,831)	$ (188,632)	$ (67,395)
Net loss per share, basic (in dollars per share)	$ (0.82)	$ (0.29)	$ (2.46)	$ (0.91)
Net loss per share, diluted (in dollars per share)	$ (0.82)	$ (0.29)	$ (2.46)	$ (0.91)
Weighted-average shares of common stock outstanding, basic (in shares)	77,059,157	74,421,911	76,667,681	74,051,220
Weighted-average shares of common stock outstanding, diluted (in shares)	77,059,157	74,421,911	76,667,681	74,051,220
Other comprehensive income (loss)
Foreign currency translation adjustments, net of tax of $0 for all periods presented	$ (7,674)	$ 2,977	$ (345)	$ 2,172
Comprehensive loss	$ (70,526)	$ (18,854)	$ (188,977)	$ (65,223)