Revenue Recognition (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Revenues	$ 160,945	$ 108,512	$ 392,082	$ 336,144
Instruction and educational support	93,290	59,755	221,756	184,821
Provision (benefit) for income taxes	(3,236)	2,138	(1,643)	13,670
Net income (loss)	(52,781)	$ 6,227	(38,126)	$ 27,107
Tuition receivable - net	52,527		52,527		$ 23,122
Other current assets	17,367		17,367		11,293
Income taxes receivable	6,995		6,995
Retained earnings	106,907		106,907		$ 162,006
Accounting Standards Update 2014-09
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Impact of adoption of new accounting standards	(171)		(171)
Accounting Standards Update 2014-09 | Balances without Adoption of ASC 606
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Revenues	160,294		391,181
Instruction and educational support	92,626		220,745
Provision (benefit) for income taxes	(3,233)		(1,613)
Net income (loss)	(52,771)		(38,046)
Tuition receivable - net	50,529		50,529
Other current assets	19,713		19,713
Income taxes receivable	6,899		6,899
Retained earnings	107,159		107,159
Accounting Standards Update 2014-09 | Effect of Change Higher/Lower
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Revenues	651		901
Instruction and educational support	664		1,011
Provision (benefit) for income taxes	(3)		(30)
Net income (loss)	(10)		(80)
Tuition receivable - net	1,998		1,998
Other current assets	(2,346)		(2,346)
Income taxes receivable	96		96
Retained earnings	$ (252)		$ (252)