Equity Compensation - Stock-Based Compensation Expense and Related Income Tax Benefit (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock-based compensation expense	$ 1,364	$ 2,311	$ 3,260	$ 4,862
Income tax (benefit)	(525)	(890)	(1,255)	(1,872)
Cost of Educational Services [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock-based compensation expense	703	1,119	1,645	2,337
Student Services and Administrative Expenses [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock-based compensation expense	$ 661	$ 1,192	$ 1,615	$ 2,525