Variable Interest Entities - Schedule of Carrying Value of Assets and Liabilities Eliminated from Financial Statement (Detail) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2014	Dec. 31, 2013	Sep. 30, 2013	Feb. 28, 2013
Variable Interest Entity [Line Items]
Total assets	$ (767,506)	$ (806,851)	$ (739,302)
Other current liabilities	(27,838)	(42,136)	(57,485)
Total	(635,971)	(691,205)	(598,067)
PEAKS Trust [Member]
Variable Interest Entity [Line Items]
Total assets	(68,862)	(86,802)	(94,175)	(113,819)
Other current liabilities	(287)	(697)	(496)	(471)
Total	(140,803)	(229,921)	(228,991)	(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				$ 46,114