Business Combinations - Fair Value of Assets and Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Nov. 03, 2020	Dec. 31, 2019	Dec. 31, 2018	Aug. 01, 2018
Fair value of assets and liabilities
Goodwill	$ 1,318,526		$ 732,075	$ 732,540
Torrens University and Related Assets in Australia and New Zealand (ANZ)
Fair value of assets and liabilities
Cash and cash equivalents		$ 16,082
Tuition receivable		24,447
Other current assets		17,713
Property and equipment, net		41,770
Right-of-use lease assets		44,229
Intangible assets		103,161
Goodwill		546,053
Other assets		2,799
Total assets acquired		796,254
Accounts payable and accrued expenses		(33,876)
Income taxes payable		(229)
Contract liabilities		(33,309)
Lease liabilities		(9,685)
Deferred income taxes		(18,712)
Lease liabilities, non-current		(34,544)
Other long-term liabilities		(7,520)
Total liabilities assumed		(137,875)
Total consideration		$ 658,379
Capella Merger
Fair value of assets and liabilities
Cash and cash equivalents					$ 167,859
Marketable securities					31,419
Tuition receivable					36,716
Income tax receivable					163
Other current assets					9,041
Marketable securities, non-current					34,700
Property and equipment, net					53,182
Intangible assets					349,800
Goodwill					725,275
Other assets					14,556
Total assets acquired					1,422,711
Accounts payable and accrued expenses					(48,103)
Contract liabilities					(39,000)
Deferred income taxes					(96,320)
Other long-term liabilities					(2,327)
Total liabilities assumed					(185,750)
Total consideration					$ 1,236,961