Significant Accounting Policies - Additional Information (Details)	3 Months Ended								12 Months Ended
	Dec. 31, 2018 USD ($) country entity	Sep. 30, 2018 USD ($)	Jun. 30, 2018 USD ($)	Mar. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	Sep. 30, 2017 USD ($)	Jun. 30, 2017 USD ($)	Mar. 31, 2017 USD ($)	Dec. 31, 2018 USD ($) country entity	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)	Jan. 01, 2018 USD ($)
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Revenues	$ 913,710,000	$ 787,102,000	$ 1,017,196,000	$ 632,216,000	$ 951,189,000	$ 818,601,000	$ 1,017,108,000	$ 598,978,000	$ 3,350,224,000	$ 3,385,876,000	$ 3,301,864,000
Cash and cash equivalents	388,490,000				320,567,000				$ 388,490,000	320,567,000	295,785,000
Receivables deemed uncollectible, period									2 years
Income (loss) from discontinued operations, net of tax	56,621,000	$ (34,466,000)	$ 38,072,000	$ 18,853,000	28,879,000	$ (36,309,000)	$ 33,943,000	$ 46,413,000	$ 79,080,000	72,926,000	33,446,000
Deferred online course development costs	57,065,000				57,995,000				57,065,000	57,995,000
Deferred accreditation costs	2,734,000				2,936,000				2,734,000	2,936,000
Deferred costs, gross	184,855,000				164,552,000				184,855,000	164,552,000
Accumulated amortization of deferred costs	(118,020,000)				(103,621,000)				(118,020,000)	(103,621,000)
Unamortized balances of deferred financing costs	88,241,000				105,299,000				88,241,000	105,299,000
Advertising costs									232,317,000	222,724,000	221,482,000
Cumulative effect of adoption to retained earnings	(530,919,000)				(946,236,000)				(530,919,000)	(946,236,000)
Net Cash Provided by (Used in) Operating Activities									396,858,000	192,157,000	192,256,000
Net Cash Provided by (Used in) Investing Activities, Continuing Operations									115,494,000	(284,682,000)	297,297,000
Accounting Standards Update 2014-09 | Difference between Revenue Guidance in Effect before and after Topic 606
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Revenues									0
Cumulative effect of adoption to retained earnings	6,697,000								6,697,000			$ 1,400,000
Accounting Standards Update 2014-09 | Pro Forma | Difference between Revenue Guidance in Effect before and after Topic 606
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative effect of adoption to retained earnings	$ 2,000,000								2,000,000
Accounting Standards Update 2016-15
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Net Cash Provided by (Used in) Operating Activities									$ (65,000,000)
Accounting Standards Update 2016-16
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative effect of adoption to retained earnings												$ 44,000,000
Accounting Standards Update 2016-18
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Net Cash Provided by (Used in) Operating Activities										(4,000)	8,000
Net Cash Provided by (Used in) Investing Activities, Continuing Operations										39,848,000	28,000
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]
Undistributed foreign earnings	$ 2,500,000								$ 2,500,000
Revenues									493,008,000	450,719,000	389,815,000
Chile
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Revenues									$ 654,002,000	617,213,000	564,592,000
Variable Interest Entity, Primary Beneficiary
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Number of consolidated entities (entity) | entity									11
Number of countries with variable interest entities (country) | country	7								7
Revenues									$ 100,227,000	123,237,000	113,276,000
Cash and cash equivalents	$ 158,387,000				100,971,000				158,387,000	100,971,000
Income (loss) from discontinued operations, net of tax									$ 86,887,000	30,145,000	29,724,000
Variable Interest Entity, Primary Beneficiary | Chile
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Number of entities with cash balances (entity) | entity	3								3
Variable Interest Entity, Primary Beneficiary | Central America & U.S. Campuses
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Non-operating investment income									$ 14,331,000	11,696,000	$ 11,061,000
Continuing Operations | Variable Interest Entity, Primary Beneficiary
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Number of consolidated entities (entity) | entity									5
Discontinued Operations | Variable Interest Entity, Primary Beneficiary
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Number of consolidated entities (entity) | entity									6
Commission and Bonuses
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Capitalized Contract Cost, Net	$ 7,036,000				$ 0				$ 7,036,000	$ 0