Employee Pension Benefits - Schedule of Net Periodic Pension Benefit and Related Income Statement Line Item (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Defined Benefit Plan Disclosure [Line Items]
Net periodic pension benefit	$ 1,344	$ 1,194	$ 4,070	$ 3,583
Cost of Educational Services [Member]
Defined Benefit Plan Disclosure [Line Items]
Net periodic pension benefit	841	787	2,603	2,349
Student Services and Administrative Expenses [Member]
Defined Benefit Plan Disclosure [Line Items]
Net periodic pension benefit	$ 503	$ 407	$ 1,467	$ 1,234