Condensed Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016
Statement Of Financial Position [Abstract]
Student receivables, allowance for doubtful accounts, current	$ 22,162	$ 21,376
Property and equipment, accumulated depreciation	376,892	381,415
Intangible assets, amortization	1,000	800
Student receivables, allowance for doubtful accounts, non-current	$ 1,991	$ 1,766
Preferred stock, par value	$ 0.01	$ 0.01
Preferred stock, shares authorized	1,000,000	1,000,000
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Common stock, par value	$ 0.01	$ 0.01
Common stock, shares authorized	300,000,000	300,000,000
Common stock, shares issued	83,906,099	83,538,033
Common stock, shares outstanding	68,770,300	68,519,005
Treasury, Shares in treasury	15,135,799	15,019,028