Equity Compensation - Stock-Based Compensation Expense and Related Income Tax Benefit (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock-based compensation expense	$ 1,266	$ 2,667	$ 4,526	$ 7,529
Income tax (benefit)	(487)	(1,027)	(1,742)	(2,899)
Cost of Educational Services [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock-based compensation expense	700	1,211	2,345	3,548
Student Services and Administrative Expenses [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock-based compensation expense	$ 566	$ 1,456	$ 2,181	$ 3,981