Consolidated Statements of Cash Flows (Unaudited) - USD ($)	6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020
Operating activities
Net income	$ 98,775,000	$ 22,138,000
Adjustments to reconcile net income to net cash provided by operating activities:
Provision for loan losses	0	53,250,000
Depreciation, amortization and accretion	22,459,000	13,247,000
Deferred income tax expense (benefit)	4,975,000	(9,812,000)
Funding of mortgage loans held for sale	(2,222,822,000)	(2,023,834,000)
Proceeds from sales of mortgage loans held for sale	2,249,240,000	2,070,701,000
Gains on sales of mortgage loans held for sale	(51,482,000)	(68,342,000)
Valuation adjustment to mortgage servicing rights	(13,561,000)	14,522,000
Gains on sales of securities	(1,357,000)	(31,000)
Penalty on prepayment of debt	0	90,000
(Gains) losses on sales of premises and equipment	(687,000)	35,000
Stock-based compensation expense	5,142,000	5,748,000
Increase in other assets	(15,117,000)	(68,031,000)
(Decrease) increase in other liabilities	(25,985,000)	45,232,000
Net cash provided by operating activities	49,580,000	54,913,000
Investing activities
Purchases of securities available for sale	(1,190,400,000)	(182,745,000)
Proceeds from sales of securities available for sale	155,391,000	8,773,000
Proceeds from call/maturities of securities available for sale	195,114,000	183,807,000
Net decrease (increase) in loans	783,838,000	(1,296,880,000)
Purchases of premises and equipment	(12,953,000)	(3,856,000)
Proceeds from sales of premises and equipment	8,715,000	0
Purchase of bank-owned life insurance	(45,000,000)	0
Net change in FHLB stock	(1,207,000)	(496,000)
Proceeds from sales of other assets	3,378,000	2,228,000
Other, net	2,803,000	0
Net cash used in investing activities	(100,321,000)	(1,289,169,000)
Financing activities
Net increase in noninterest-bearing deposits	664,087,000	1,188,526,000
Net increase in interest-bearing deposits	392,183,000	444,810,000
Net decrease in short-term borrowings	(6,407,000)	(147,281,000)
Repayment of long-term debt	(1,733,000)	(177,000)
Cash paid for dividends	(25,104,000)	(25,080,000)
Repurchase of shares in connection with stock repurchase program	0	(24,569,000)
Net cash provided by financing activities	1,023,026,000	1,436,229,000
Net increase in cash and cash equivalents	972,285,000	201,973,000
Cash and cash equivalents at beginning of period	633,203,000	414,930,000
Cash and cash equivalents at end of period	1,605,488,000	616,903,000
Supplemental disclosures
Cash paid for interest	24,146,000	43,564,000
Cash paid for income taxes	31,443,000	16,163,000
Noncash transactions:
Transfers of loans to other real estate owned	2,503,000	4,259,000
Financed sales of other real estate owned	130,000	154,000
Recognition of operating right-of-use assets	3,624,000	4,235,000
Recognition of operating lease liabilities	$ 3,624,000	$ 2,766,000