Significant Accounting Policies - Tuition Receivable (Details) - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016	Mar. 31, 2016	Dec. 31, 2015
Schedule of tuition receivable and allowance for doubtful accounts
Tuition receivable	$ 31,143	$ 30,733
Allowance for doubtful accounts	(10,820)	(10,201)	$ (10,226)	$ (10,024)
Tuition receivable, net	20,323	20,532
Other Assets [Member]
Schedule of tuition receivable and allowance for doubtful accounts
Tuition receivable included in other assets	$ 2,400	$ 2,300