Variable Interest Entities - Schedule of Carrying Value of Assets and Liabilities Eliminated from Financial Statement (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Feb. 28, 2013
Variable Interest Entity [Line Items]
Total assets	$ (749,160)	$ (806,851)
Other current liabilities	(27,050)	(42,136)
Total liabilities	(601,155)	(691,205)
PEAKS Trust [Member]
Variable Interest Entity [Line Items]
Total assets	(68,627)	(86,802)	(113,819)
Other current liabilities	(199)	(697)	(471)
Total liabilities	(76,402)	(229,921)	(226,567)
PEAKS Trust [Member] | Consolidation, Eliminations [Member]
Variable Interest Entity [Line Items]
Other assets			6,614
Total assets			6,614
Other current liabilities			3,060
Other liabilities			43,054
Total liabilities			$ 46,114