Private Education Loans - Schedule of Information Regarding Changes in Allowance for Loan Losses (Detail) - USD ($) $ in Thousands	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
Accounts, Notes, Loans and Financing Receivable [Line Items]
Provision for loan losses	$ 568	$ 4,511	$ 9,071	$ 0	$ 8,648	$ 16,382	$ 4,319	$ 0	$ 14,150	$ 29,349	$ 0
PEAKS Trust Student Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Balance at beginning of period				29,349				$ 0	29,349	0
Loans charged off									(1,199)	0
Recoveries from charged off loans									2,092	0
Provision for loan losses									12,111	29,349
Balance at end of period	42,353				29,349				42,353	29,349	$ 0
CUSO Student Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Balance at beginning of period				$ 0					0
Loans charged off									0
Recoveries from charged off loans									0
Provision for loan losses									2,039
Balance at end of period	$ 2,039				$ 0				$ 2,039	$ 0