CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Operating activities
Net income	$ 274,284	$ 193,785	$ 257,593
Adjustments to reconcile net income to net cash (used in) provided by operating activities:
Provisions for credit losses	90,055	85,529	69,339
Deferred tax (benefit) provision	(77,227)	(40,888)	14,567
Amortization of brokered deposit placement fee	10,510	10,164	9,754
Amortization of ABCP upfront fee	2,337	0	0
Amortization of deferred loan origination costs and fees, net	3,746	1,995	2,199
Net amortization of discount on investments	1,716	633	(7,187)
Interest income on tax indemnification receivable	(5,398)	(5,904)	0
Depreciation of premises and equipment	7,437	6,099	5,059
Amortization and impairment of acquired intangibles	1,480	3,290	3,317
Stock-based compensation expense	21,598	24,971	15,681
Unrealized (gains)/losses on derivative and hedging activities, net	(2,500)	1,214	(324)
Gains on sale of securities	0	0	(63,813)
Gains on sale of loans, net	(135,358)	(121,359)	(196,593)
Other adjustments to net income, net	(306)	0	1,046
Changes in operating assets and liabilities:
Net decrease in loans held for sale	55	6,519	3,628
Origination of loans held for sale	(55)	(6,519)	(3,628)
Increase in accrued interest receivable	(377,648)	(331,014)	(281,856)
(Increase) decrease in restricted cash and investments, net	(737)	(493)	136
Decrease (increase) in other interest-earning assets	17,634	(72,435)	(39)
Decrease in tax indemnification receivable	59,633	44,724	0
Increase in other assets	(18,070)	(24,959)	(2,357)
Increase (decrease) in income tax payable, net	56,813	(221,222)	56,784
Increase in accrued interest payable	303	2,985	239
(Decrease) increase in payable due to entity that is a subsidiary of Navient	(6,774)	8,764	147,379
(Decrease) increase in other liabilities	(14,731)	(2,652)	39,096
Total adjustments	(365,487)	(630,558)	(187,573)
Total net cash (used in) provided by operating activities	(91,203)	(436,773)	70,020
Investing activities
Loans acquired and originated	(4,366,651)	(4,094,790)	(4,387,093)
Net proceeds from sales of loans held for investment	1,547,373	2,001,625	2,546,940
Proceeds from claim payments	111,580	127,869	82,615
Net decrease in loans held for investment	913,005	638,321	490,791
Increase in restricted cash and investment - variable interest entities	(22,439)	0	0
Purchases of available-for-sale securities	(64,112)	(72,049)	(62,097)
Proceeds from sales and maturities of available-for-sale securities	33,735	10,653	597,728
Total net cash used in investing activities	(1,847,509)	(1,388,371)	(731,116)
Financing activities
Brokered deposit placement fee	(4,098)	(15,098)	(12,114)
Net increase in certificates of deposit	611,643	340,225	535,456
Net increase in other deposits	324,518	1,207,487	1,126,673
Borrowings collateralized by loans in securitization trusts - issued	620,681	0	0
Borrowings collateralized by loans in securitization - repaid	(41,976)	0	0
Borrowings under ABCP facility	1,210,180	0	0
Repayment of borrowings under ABCP facility	(710,005)	0	0
Fees paid - ABCP facility	(2,337)	0	0
Net decrease in deposits with entity that is a subsidiary of Navient	0	(5,633)	(126,923)
Special cash contribution from Navient	0	472,718	0
Net capital contributions from entity that is a subsidiary of Navient	0	12,022	(164,471)
Excess tax benefit from the exercise of stock-based awards	6,140	3,271	6,258
Preferred stock dividends paid	(19,595)	(12,933)	0
Dividend paid to entity that is a subsidiary of Navient	0	0	(120,000)
Net cash provided by financing activities	1,995,151	2,002,059	1,244,879
Net increase in cash and cash equivalents	56,439	176,915	583,783
Cash and cash equivalents at beginning of year	2,359,780	2,182,865	1,599,082
Cash and cash equivalents at end of year	2,416,219	2,359,780	2,182,865
Cash disbursements made for:
Interest	111,563	90,329	76,901
Income taxes paid	205,698	401,834	81,194
Income taxes cash received	$ (25,151)	$ (3,015)	$ 0