Discontinued Operations and Assets Held for Sale - Summary of Major Classes of Assets and Liabilities Reclassified to Held for Sale (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Assets of Discontinued Operations
Subtotal: assets of Discontinued Operations	$ 20,263	$ 1,917,435
Liabilities of Discontinued Operations
Total liabilities held for sale	16,620	702,256
Discontinued operations
Liabilities of Discontinued Operations
Deferred revenue and student deposits	198	87,793
Operating leases, including current portion	12,034	151,413
Long-term debt, seller notes and finance leases, including current portion	0	171,451
Other liabilities	4,388	291,599
Discontinued Operations, Held-for-sale
Assets of Discontinued Operations
Cash and cash equivalents	3,157	270,164
Receivables, net	1,000	113,386
Property and equipment, net	8,645	259,471
Goodwill and Tradenames	0	1,202,496
Operating lease right-of-use assets, net	6,892	136,806
Other assets	569	183,742
Valuation allowance on held-for-sale disposal groups	$ 0	$ (248,630)