CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Operating activities
Net income	$ 880,690	$ 578,276	$ 487,476
Adjustments to reconcile net income to net cash (used in) provided by operating activities:
Provisions for credit losses	93,133	354,249	244,864
Deferred tax provision (benefit)	72,776	(9,714)	(63,301)
Amortization of brokered deposit placement fee	19,401	17,788	13,055
Amortization of Secured Borrowing Facility upfront fee	2,976	1,117	1,128
Amortization of deferred loan origination costs and loan premium/(discounts), net	24,152	13,049	10,905
Net amortization of discount on investments	6,350	2,069	1,712
Reduction of tax indemnification receivable	9,066	11,649	92,815
Depreciation of premises and equipment	15,066	14,669	13,829
Stock-based compensation expense	36,464	30,600	31,524
Unrealized (gains) losses on derivative and hedging activities, net	(10,333)	(19,046)	(1,353)
Gains on sale of loans, net	(238,315)	0	(2,060)
Losses on sales of securities, net	0	0	1,549
Gain on sale of Upromise subsidiary, net	(11,331)	0	0
Other adjustments to net income, net	8,810	3,724	7,446
Changes in operating assets and liabilities:
Increase in accrued interest receivable	(876,703)	(963,885)	(864,461)
Increase in non-marketable securities	(839)	(10,700)	(5,000)
Decrease (increase) in other interest-earning assets	9,690	(25,407)	(5,571)
Decrease in tax indemnification receivable	0	0	35,989
Increase in other assets	(50,454)	(3,091)	(64,777)
Decrease in income tax payable, net	(45,611)	(30,191)	(79,693)
(Decrease) increase in accrued interest payable	(14,602)	13,817	25,979
Decrease in Upromise member accounts due to sale	(193,840)	0	0
Increase in other liabilities	80,785	5,386	15,204
Total adjustments	(1,063,359)	(593,917)	(590,217)
Total net cash used in operating activities	(182,669)	(15,641)	(102,741)
Investing activities
Loans acquired and originated	(5,378,283)	(6,138,105)	(6,493,367)
Net proceeds from sales of loans held for investment	3,875,737	0	44,832
Proceeds from claim payments	28,709	42,869	54,659
Net decrease in loans held for investment	3,832,991	4,094,021	3,076,992
Purchases of available-for-sale securities	(2,083,261)	(356,414)	(15,876)
Proceeds from sales and maturities of available-for-sale securities	654,515	50,915	77,897
Proceeds from the sale of Upromise subsidiary, net	16,922	0	0
Total net cash provided by (used in) investing activities	947,330	(2,306,714)	(3,254,863)
Financing activities
Brokered deposit placement fee	(4,810)	(27,978)	(25,785)
Net (decrease) increase in certificates of deposit	(2,428,094)	4,349,741	2,525,040
Net increase in other deposits	704,382	923,793	918,420
Borrowings collateralized by loans in securitization trusts - issued	1,338,641	1,105,594	1,891,027
Borrowings collateralized by loans in securitization trusts - repaid	(1,003,327)	(1,042,892)	(888,640)
Borrowings under Secured Borrowing Facility	0	297,800	300,000
Repayment of borrowings under Secured Borrowing Facility	(289,230)	(8,570)	(300,000)
Fees paid - Secured Borrowing Facility	(3,256)	(1,116)	(1,098)
Unsecured debt issued	495,000	0	0
Preferred stock dividends paid	(9,734)	(16,837)	(15,640)
Repurchase of Series B Preferred Stock	(68,055)	0	0
Common stock dividends paid	(46,351)	(51,114)	0
Common stock repurchased	(558,167)	(167,201)	0
Net cash (used in) provided by financing activities	(1,875,712)	5,361,220	4,403,324
Net (decrease) increase in cash, cash equivalents and restricted cash	(1,111,051)	3,038,865	1,045,720
Cash, cash equivalents and restricted cash at beginning of year	5,720,760	2,681,895	1,636,175
Cash, cash equivalents and restricted cash at end of year	4,609,709	5,720,760	2,681,895
Cash disbursements made for:
Interest	517,444	666,018	472,459
Income taxes paid	248,122	201,792	228,074
Income taxes refunded	(6,219)	(853)	(13,449)
Reconciliation of the Consolidated Statements of Cash Flows to the Consolidated Balance Sheets:
Total cash, cash equivalents and restricted cash	5,720,760	2,681,895	2,681,895
Collateralized Securities
Financing activities
Issuance costs for unsecured debt offering	(1,402)	0	0
Unsecured Debt
Financing activities
Issuance costs for unsecured debt offering	$ (1,309)	$ 0	$ 0