Variable Interest Entities - Schedule of Carrying Value of the Assets and Liabilities Eliminated from Financial Statement Related to the CUSO (Detail) - USD ($) $ in Thousands	Jun. 30, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014
Variable Interest Entity [Line Items]
Prepaid expenses and other current assets	$ (57,294)	$ (57,923)		$ (36,056)
Total assets	(711,300)	(749,160)		(776,219)
Other current liabilities	(27,288)	(27,050)		(46,233)
Total liabilities	(556,205)	(601,155)		$ (656,081)
CUSO [Member]
Variable Interest Entity [Line Items]
Total assets	(25,601)	(26,606)	$ (30,136)
Other current liabilities	(302)	(179)	(624)
Other liabilities	(1,879)	(1,073)	(1,940)
Total liabilities	$ (113,270)	$ (122,259)	(125,106)
Consolidation, Eliminations [Member] | CUSO [Member]
Variable Interest Entity [Line Items]
Prepaid expenses and other current assets			3,260
Total assets			3,260
Other current liabilities			23,887
Other liabilities			90,974
Total liabilities			$ 114,861