Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Cash Flows From Operating Activities
Net income	$ 154,244	$ 194,451	$ 172,882
Adjustments to reconcile net income to net cash provided by operating activities:
Provision for credit losses	77,700	3,493	14,769
Stock-based compensation expense	10,737	9,271	8,354
Depreciation, amortization and accretion	14,893	34,213	32,971
Investment securities loss (gain), net	(16,710)	(2,132)	89
Net realized loss (gain) on sale of premises and equipment and OPPO	(1,334)	(7,317)	316
Net realized loss (gain) on sale and valuation adjustments of OREO	34	602	(1,218)
Gain on bank owned life insurance death benefit	0	(3,051)	0
Originations of loans held for sale	(491,385)	(210,484)	(133,945)
Proceeds from sale of loans held-for-sale	483,130	196,615	135,862
Change in Fair Value of Loans Held-for-sale	(508)	0	0
Deferred income tax expense	(13,768)	330	108
Net change in:
Interest receivable	(7,992)	(1,516)	(4,442)
Interest payable	(933)	632	164
Other assets	(48,539)	(23,464)	2,176
Other liabilities	32,791	14,308	6,679
Net cash provided by operating activities	192,292	204,747	237,201
Cash Flows From Investing Activities
Loans originated, net of principal collected	(619,543)	(291,857)	2,069
Purchases of debt securities available for sale	(2,118,667)	(1,196,895)	(965,585)
Purchases of loans held for investment	50,035	57,075	46,969
Purchases of premises and equipment	(8,720)	(8,447)	(11,328)
Purchases of Federal Home Loan Bank stock	(53,240)	(273,800)	(197,440)
Proceeds from Sale of Debt Securities, Available-for-sale	194,697	259,554	32,330
Proceeds from sale of equity securities	3,000	0	4,808
Proceeds from principal repayments and maturities of securities available for sale	603,129	428,025	465,747
Proceeds from sales of premises and equipment	2,948	8,634	16,030
Proceeds from redemption of Federal Home Loan Bank Stock	91,080	251,640	181,920
Proceeds from sales of other real estate owned and other personal property owned	1,074	6,506	7,261
Proceeds from bank owned life insurance death benefit	1,050	8,265	5,074
Proceeds from Termination of Cash Flow Hedging Instrument	34,442	0	0
Net cash used in investing activities	(1,918,785)	(865,450)	(506,083)
Cash Flows From Financing Activities
Net increase (decrease) in deposits	3,185,167	226,958	(73,591)
Net increase in sweep repurchase agreements	9,422	3,343	7,035
Proceeds from exercise of stock options and employee stock purchase plan	2,028	2,025	1,857
Proceeds from Federal Home Loan Bank advances	1,331,000	6,845,000	4,936,000
Proceeds from Federal Reserve Bank borrowings	222,010	36,000	5,010
Proceeds from other borrowings	9,222	100	0
Payments for Federal Home Loan Bank advances	(2,277,000)	(6,291,000)	(4,548,000)
Payments for Federal Reserve Bank borrowings	(222,010)	(36,000)	(5,010)
Payments for other borrowings	(9,222)	(100)	0
Payments for common stock dividends	(95,509)	(101,911)	(83,440)
Repayment of junior subordinated debentures	0	0	8,248
Repayment of term repurchase agreement	0	0	(25,000)
Payments for purchase of treasury stock	(20,000)	(50,834)	0
Payments for purchase and retirement of common stock	2,522	2,792	2,677
Net cash provided by financing activities	2,132,586	630,789	203,936
Increase (decrease) in cash and cash equivalents	406,093	(29,914)	(64,946)
Cash and cash equivalents at beginning of period	247,673	277,587	342,533
Supplemental Information:
Interest paid	18,631	35,916	18,066
Income taxes paid, net of refunds	43,287	47,375	24,067
Non-cash investing and financing activities:
Loans transferred to OREO	1,033	386	1,200
Premises and equipment expenditures incurred but not yet paid	302	451	195
Change in dividends payable on unvested shares included in other liabilities	$ 706	$ 354	$ 19