Significant Accounting Policies - Additional Information (Details) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019 USD ($) country	Sep. 30, 2019 USD ($)	Jun. 30, 2019 USD ($)	Mar. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)	Sep. 30, 2018 USD ($)	Jun. 30, 2018 USD ($)	Mar. 31, 2018 USD ($)	Dec. 31, 2019 USD ($) entity country	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	Jan. 01, 2019 USD ($)
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Revenues	$ 883,152	$ 773,699	$ 992,403	$ 601,072	$ 892,451	$ 778,255	$ 1,005,229	$ 614,278	$ 3,250,326	$ 3,290,213	$ 3,333,073
Income from discontinued operations, net of tax	(12,531)	$ (27,137)	$ 30,280	$ 63,329	61,333	$ (37,905)	$ 37,542	$ 23,914	$ 53,941	84,884	77,390
Receivables deemed uncollectible, period									2 years
Deferred online course development costs	55,728				57,065				$ 55,728	57,065
Deferred accreditation costs	2,697				2,734				2,697	2,734
Deferred costs, gross	209,163				184,855				209,163	184,855
Accumulated amortization of deferred costs	139,165				118,020				139,165	118,020
Unamortized balances of deferred financing costs	66,069				88,241				66,069	88,241
Advertising costs									227,399	232,282	222,679
Operating lease right-of-use assets, net	861,878				0				861,878	0
Operating lease liabilities	$ 883,916								883,916
Operating lease, expense									$ 13
Minimum
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Contract cost, amortization period	2 years								2 years
Maximum
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Contract cost, amortization period	4 years								4 years
Peru
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Revenues									$ 545,291	493,008	450,719
Undistributed foreign earnings					2,500					2,500
Variable Interest Entity, Primary Beneficiary
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Number of consolidated entities (entity) | entity									5
Number of countries with variable interest entities (country) | country	3								3
Revenues									$ 39,005	100,227	123,237
Income from discontinued operations, net of tax									9,577	86,887	30,145
Operating lease right-of-use assets, net	$ 65,761				0				$ 65,761	0
Variable Interest Entity, Primary Beneficiary | Central America & U.S. Campuses
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Non-operating investment income										14,331	$ 11,696
Continuing operations | Variable Interest Entity, Primary Beneficiary
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Number of consolidated entities (entity) | entity									4
Discontinued operations | Variable Interest Entity, Primary Beneficiary
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Number of consolidated entities (entity) | entity									1
Commission and Bonuses
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Capitalized contract cost, net	$ 11,573				$ 7,036				$ 11,573	$ 7,036
(Accumulated deficit) retained earnings
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative-effect adjustment upon adoption												$ 28,944