Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Statement Of Financial Position [Abstract]
Student receivables, allowance for doubtful accounts, current	$ 18,013	$ 14,842
Student receivables, allowance for doubtful accounts, non-current	$ 2,216	$ 4,255
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	82,996,585	82,336,689
Common stock, shares outstanding	68,098,654	67,521,038
Treasury, Shares in treasury	14,897,931	14,815,651