Variable Interest Entities - Schedule of Carrying Value of the Assets and Liabilities Eliminated from Financial Statement Related to the CUSO (Detail) - USD ($) $ in Thousands	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Mar. 31, 2014
Variable Interest Entity [Line Items]
Prepaid expenses and other current assets	$ (56,068)	$ (57,923)		$ (34,686)
Total assets	(740,258)	(752,838)		(780,332)
Other current liabilities	(28,602)	(27,153)		(52,268)
Total liabilities	(592,335)	(610,766)		$ (664,089)
CUSO [Member]
Variable Interest Entity [Line Items]
Total assets	(24,990)	(26,606)	$ (30,136)
Other current liabilities	(182)	(179)	(624)
Other liabilities	(1,776)	(1,073)	(1,940)
Total liabilities	$ (119,147)	$ (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