Variable Interest Entities - Guarantee and Other Payments Related to PEAKS Program (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014	Dec. 31, 2014
Variable Interest Entity [Line Items]
PEAKS Guarantee					$ 159,300
Payments on Behalf of Borrowers					$ 1,832
PEAKS Program [Member]
Variable Interest Entity [Line Items]
PEAKS Guarantee	$ 6,820	$ 1,088	$ 20,457	$ 41,801
Payments on Behalf of Borrowers	0	0	0	1,832
Total	$ 6,820	$ 1,088	$ 20,457	$ 43,633