Significant Accounting Policies - Tuition Receivable (Details) - USD ($) $ in Thousands	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014
Schedule of tuition receivable and allowance for doubtful accounts
Tuition receivable	$ 29,034		$ 28,543
Allowance for doubtful accounts	(9,981)	$ (10,226)	(10,024)	$ (8,733)	$ (8,688)	$ (8,835)
Tuition receivable, net	19,053		18,519
Other Assets [Member]
Schedule of tuition receivable and allowance for doubtful accounts
Tuition receivable included in other assets	$ 2,000		$ 2,000