CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Operating activities
Net income	$ 322,866	$ 300,824	$ 197,063
Adjustments to reconcile net income to net cash provided by operating activities:
Provision for credit losses	75,000	87,000	44,000
Deferred tax expense (benefit)	10,796	(6,400)	31,276
Depreciation and amortization	37,267	32,022	27,871
Net (gain)/loss on sale of loans held for sale	20,259	15,934	2,387
Increase (decrease) in valuation allowance on mortgage servicing rights	5,803	(2,823)	2,823
Stock-based compensation expense	17,604	16,938	22,019
Purchases and originations of loans held for sale	(10,183,057)	(6,753,709)	(5,556,964)
Proceeds from sales and repayments of loans held for sale	9,508,927	5,759,067	5,457,117
Other real estate owned write-down		6,100
Changes in operating assets and liabilities:
Accrued interest receivable and other assets	(143,617)	(123,542)	(105,720)
Accrued interest payable and other liabilities	87,884	(5,026)	10,289
Net cash (used in)/provided by operating activities	(240,268)	(679,715)	132,161
Investing activities
Purchases of investment securities	(113,233)	(101,558)	(97,776)
Maturities and calls of available-for-sale securities	0	0	94,775
Principal payments received on investment securities	6,185	3,426	4,383
Originations of mortgage finance loans	(138,759,289)	(99,151,237)	(86,931,566)
Proceeds from pay-offs of mortgage finance loans	136,466,964	98,581,873	86,120,744
Net (increase)/decrease in loans held for investment, excluding mortgage finance loans	139,868	(1,402,068)	(2,395,063)
Purchase of premises and equipment, net	(16,651)	(7,651)	(12,265)
Proceeds from sale of mortgage servicing rights	0	70,824	0
Proceeds from sale of MSRs	79	13,645	1,023
Net cash used in investing activities	(2,276,077)	(1,992,746)	(3,215,745)
Financing activities
Net increase in deposits	5,872,480	1,482,933	2,106,349
Costs from issuance of stock related to stock-based awards and warrants	(1,459)	(2,382)	(2,241)
Preferred dividends paid	(9,750)	(9,750)	(9,750)
Net increase/(decrease) in other borrowings	(1,500,000)	1,100,000	800,000
Net increase/(decrease) in federal funds purchased and repurchase agreements	(499,408)	276,134	255,465
Net cash provided by financing activities	3,861,863	2,846,935	3,149,823
Net increase in cash and cash equivalents	1,345,518	174,474	66,239
Cash and cash equivalents at beginning of period	3,080,065	2,905,591	2,839,352
Cash and cash equivalents at end of period	4,425,583	3,080,065	2,905,591
Supplemental disclosures of cash flow information:
Cash paid during the period for interest	393,507	236,338	115,789
Cash paid during the period for income taxes	$ 89,967	$ 75,405	$ 103,871