Variable Interest Entities - Schedule of Revenue and Expenses of PEAKS Trust (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
Variable Interest Entity [Line Items]
Student services and administrative expenses	$ 91,891	$ 100,440	$ 97,547	$ 99,238	$ 101,303	$ 96,182	$ 98,335	$ 101,721	$ 389,116	$ 397,541	$ 400,856
Provision for private education loan losses	568	4,511	9,071	0	8,648	16,382	4,319	0	14,150	29,349	0
Interest expense	9,305	5,831	6,263	6,901	7,144	7,190	7,369	3,574	28,300	25,277	3,723
Income (loss) before provision for income taxes	25,335	17,600	574	6,141	(53,777)	12,760	26,707	(22,926)	49,650	(37,236)	227,988
PEAKS Trust [Member]
Variable Interest Entity [Line Items]
Revenue									11,471	12,996
Student services and administrative expenses									4,479	5,288
Provision for private education loan losses									12,111	29,349
Interest expense									20,814	21,288
Income (loss) before provision for income taxes									$ (25,933)	$ (42,929)