Debt - Total Amount of Interest Expense and Discount Accretion on PEAKS Senior Debt (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Debt Instrument [Line Items]
Interest expense	$ 9,305	$ 5,831	$ 6,263	$ 6,901	$ 7,144	$ 7,190	$ 7,369	$ 3,574	$ 28,300	$ 25,277	$ 3,723
PEAKS Senior Debt [Member]
Debt Instrument [Line Items]
Interest expense									20,814	21,288
Discount accretion									$ 6,712	$ 4,926