Assets Held for Sale - Summary of Major Classes of Assets and Liabilities Reclassified to Held for Sale (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Long-term assets held for sale	$ 392,391	$ 0
Disposal Group, Held-for-sale, Not Discontinued Operations
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Deferred revenue and student deposits	94,951
Property and equipment, net	275,913
Goodwill	32,740
Tradenames	28,434
Other long-term assets	55,304
Long-term assets held for sale	392,391
Long-term debt, including current portion	53,440
Other liabilities	122,735
Total liabilities held for sale	$ 271,126