Loans Held for Investment - Student Loan Portfolio by Program (Detail) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Receivables [Abstract]
Private Education Loans	$ 17,132,907	$ 14,251,675
Deferred origination costs	53,501	44,206
Allowance for loan losses	(227,167)	(182,472)
Total Private Education Loans, net	16,959,241	14,113,409
FFELP Loans	949,180	1,010,908
Unamortized acquisition costs, net	2,696	2,941
Allowance for loan losses	(1,352)	(2,171)
Total FFELP Loans, net	950,524	1,011,678
Personal Loans	132,100	12,893
Allowance for loan losses	(1,400)	(58)
Total Personal Loans, net	130,700	12,835
Loans held for investment, net	$ 18,040,465	$ 15,137,922

Amount after allowance and deduction of deferred interest and fees, unamortized costs and premiums and discounts from face amounts, of loans and leases held in portfolio, including but not limited to, commercial and consumer loans. Excludes loans and leases covered under loss sharing agreements and loans held for sale.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=82891408&loc=d3e4428-111522

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03.7)
-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

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