Equity Compensation - Stock-Based Compensation Expense and Related Income Tax Benefit (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock-based compensation expense	$ 1,896	$ 2,551
Income tax (benefit)	(730)	(982)
Cost of Educational Services [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock-based compensation expense	942	1,218
Student Services and Administrative Expenses [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock-based compensation expense	$ 954	$ 1,333