Variable Interest Entities - Additional Information (Detail)		1 Months Ended	3 Months Ended			4 Months Ended	9 Months Ended		12 Months Ended
	Mar. 20, 2014 USD ($)	Jan. 31, 2014 USD ($)	Dec. 31, 2015 USD ($)	Sep. 30, 2015 USD ($)	Sep. 30, 2014 USD ($)	Sep. 30, 2015 USD ($)	Sep. 30, 2015 USD ($) Installment	Sep. 30, 2014 USD ($)	Dec. 31, 2014 USD ($)	Dec. 31, 2013 USD ($)
Variable Interest Entity [Line Items]
Payments on Behalf of Borrowers									$ 1,832,000
Prepayment of Senior debt									159,300,000
Gain (loss) on consolidation				$ 0	$ 16,631,000		$ 0	$ 16,631,000
Offset amounts under Revolving Note				0	0		0	0
CUSO RSA [Member]
Variable Interest Entity [Line Items]
Deferred payments				2,574,000		$ 3,402,000	3,402,000
Recoveries of charged off loans not yet received				351,000		468,000	$ 468,000	475,000	475,000
CUSO RSA [Member] | Scenario, Forecast [Member]
Variable Interest Entity [Line Items]
Deferred payments			$ 2,911,000
Recoveries of charged off loans not yet received			$ 311,000
PEAKS Trust [Member]
Variable Interest Entity [Line Items]
Payments on Behalf of Borrowers		$ 1,832,000
Prepayment of Senior debt	$ 40,000,000
CUSO [Member]
Variable Interest Entity [Line Items]
Number of monthly payments | Installment							10
Discount rate							10.00%
Gain (loss) on consolidation					16,631,000			16,631,000
Revenue or expenses on consolidation of income					0			0
Recoveries of charged off loans not yet received				0	0		$ 0
Offset amounts under Revolving Note										$ 8,472,000
Revolving note, amount owned to company				$ 8,200,000	8,200,000	$ 8,200,000	$ 8,200,000	8,200,000	$ 8,200,000
CUSO [Member] | Fair Value [Member]
Variable Interest Entity [Line Items]
Amount of liabilities exceeded assets					94,970,000			94,970,000
CUSO [Member] | Carrying Value [Member]
Variable Interest Entity [Line Items]
Amount of liabilities exceeded assets					$ 111,601,000			$ 111,601,000