CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Operating activities
Net income	$ 250,327	$ 274,284	$ 193,785
Adjustments to reconcile net income to net cash (used in) provided by operating activities:
Provisions for credit losses	159,405	90,055	85,529
Deferred tax benefit	(88,732)	(77,227)	(40,888)
Amortization of brokered deposit placement fee	10,133	10,510	10,164
Amortization of ABCP upfront fee	1,229	2,337	0
Amortization of deferred loan origination costs and fees, net	5,811	3,746	1,995
Net amortization of discount on investments	2,043	1,716	633
Interest income on tax indemnification receivable	(12,283)	(5,398)	(5,904)
Depreciation of premises and equipment	9,592	7,437	6,099
Amortization of acquired intangibles	906	1,480	3,290
Stock-based compensation expense	22,944	21,598	24,971
Unrealized losses (gains) on derivative and hedging activities, net	2,263	(2,500)	1,214
Gains on sale of loans, net	(230)	(135,358)	(121,359)
Other adjustments to net income, net	3,524	(306)	0
Changes in operating assets and liabilities:
Net decrease in loans held for sale	0	55	6,519
Origination of loans held for sale	0	(55)	(6,519)
Increase in accrued interest receivable	(582,361)	(377,648)	(331,014)
Increase in restricted cash and investments, net	(3,559)	(737)	(493)
Decrease (increase) in other interest-earning assets	5,731	17,634	(72,435)
Decrease in tax indemnification receivable	59,633	59,633	44,724
Increase in other assets	(47,162)	(18,070)	(24,959)
(Decrease) increase in income tax payable, net	(18,997)	56,813	(221,222)
Increase in accrued interest payable	3,736	303	2,985
Increase (decrease) in payable due to entity that is a subsidiary of Navient	553	(6,774)	8,764
Increase (decrease) in other liabilities	14,562	(14,731)	(2,652)
Total adjustments	(451,259)	(365,487)	(630,558)
Total net cash used in operating activities	(200,932)	(91,203)	(436,773)
Investing activities
Loans acquired and originated	(4,698,548)	(4,366,651)	(4,094,790)
Net proceeds from sales of loans held for investment	9,521	1,547,373	2,001,625
Proceeds from claim payments	64,869	111,580	127,869
Net decrease in loans held for investment	1,332,341	913,005	638,321
Increase in restricted cash and investment - variable interest entities	(22,178)	(22,439)	0
Purchases of available-for-sale securities	(55,767)	(64,112)	(72,049)
Proceeds from sales and maturities of available-for-sale securities	38,721	33,735	10,653
Total net cash used in investing activities	(3,331,041)	(1,847,509)	(1,388,371)
Financing activities
Brokered deposit placement fee	(4,371)	(4,098)	(15,098)
Net (decrease) increase in certificates of deposit	(434,740)	611,643	340,225
Net increase in other deposits	2,412,221	324,518	1,207,487
Issuance costs for collateralized borrowings	(2,090)	0	0
Borrowings collateralized by loans in securitization trusts - issued	1,775,692	620,681	0
Borrowings collateralized by loans in securitization - repaid	(187,686)	(41,976)	0
Borrowings under ABCP facility	376,325	1,210,180	0
Repayment of borrowings under ABCP facility	(876,500)	(710,005)	0
Fees paid - ABCP facility	(1,450)	(2,337)	0
Net decrease in deposits with entity that is a subsidiary of Navient	0	0	(5,633)
Special cash contribution from Navient	0	0	472,718
Net capital contributions from entity that is a subsidiary of Navient	0	0	12,022
Excess tax (expense) benefit from the exercise of stock-based awards	(1,650)	6,140	3,271
Preferred stock dividends paid	(21,204)	(19,595)	(12,933)
Net cash (used in) provided by financing activities	3,034,547	1,995,151	2,002,059
Net (decrease) increase in cash and cash equivalents	(497,426)	56,439	176,915
Cash and cash equivalents at beginning of year	2,416,219	2,359,780	2,182,865
Cash and cash equivalents at end of year	1,918,793	2,416,219	2,359,780
Cash disbursements made for:
Interest	169,854	111,563	90,329
Income taxes paid	271,721	205,698	401,834
Income taxes refunded	$ (86)	$ (25,151)	$ (3,015)