Consolidated Statements of Cash Flows - USD ($)	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Operating activities
Net income	$ 166,068,000	$ 175,892,000	$ 83,651,000
Adjustments to reconcile net income to net cash provided by operating activities:
Provision for (recovery of) credit losses	23,788,000	(1,668,000)	86,850,000
Depreciation, amortization and accretion	42,744,000	47,350,000	34,633,000
Deferred income tax expense (benefit)	2,280,000	11,411,000	(13,662,000)
Proceeds from sale of mortgage servicing rights	18,525,000	0	0
Gain on sale of mortgage servicing rights	(2,960,000)	0	0
Funding of mortgage loans held for sale	(1,679,356,000)	(4,059,927,000)	(4,479,421,000)
Proceeds from sales of mortgage loans held for sale	2,043,360,000	4,116,106,000	4,530,328,000
Gains on sales of mortgage loans held for sale	(15,803,000)	(82,399,000)	(150,406,000)
Valuation adjustment to mortgage servicing rights	0	(13,561,000)	11,726,000
Gains on sales of securities	0	(2,170,000)	(46,000)
Debt prepayment penalty	0	6,123,000	121,000
(Gains) losses on sales of premises and equipment	(239,000)	(840,000)	38,000
Stock-based compensation	11,505,000	10,074,000	10,577,000
Increase in other assets	(29,671,000)	(20,812,000)	(59,224,000)
(Decrease) increase in other liabilities	(6,196,000)	(42,920,000)	27,077,000
Net cash provided by operating activities	574,045,000	142,659,000	82,242,000
Investing activities
Purchases of securities available for sale	(713,096,000)	(2,107,934,000)	(515,657,000)
Proceeds from sales of securities available for sale	0	176,455,000	44,906,000
Proceeds from call/maturities of securities available for sale	385,507,000	458,020,000	437,981,000
Purchases of securities held to maturity	(91,803,000)	(52,135,000)	0
Proceeds from call/maturities of securities held to maturity	67,448,000	2,246,000	0
Net (increase) decrease in loans	(1,456,119,000)	910,063,000	(1,233,232,000)
Purchases of premises and equipment	(14,838,000)	(20,516,000)	(28,270,000)
Proceeds from sales of premises and equipment	1,234,000	9,813,000	0
Purchase of bank-owned life insurance	(80,000,000)	(50,000,000)	0
Net change in FHLB stock	(27,807,000)	3,980,000	18,840,000
Proceeds from sales of other assets	3,578,000	6,342,000	8,438,000
Net cash paid in acquisitions	(120,888,000)	0	0
Other, net	3,127,000	3,663,000	1,446,000
Net cash used in investing activities	(2,043,657,000)	(660,003,000)	(1,265,548,000)
Financing activities
Net (decrease) increase in noninterest-bearing deposits	(159,368,000)	1,033,076,000	1,133,278,000
Net (decrease) increase in interest-bearing deposits	(259,390,000)	813,567,000	712,781,000
Net increase (decrease) in short-term borrowings	668,805,000	(7,393,000)	(467,872,000)
Proceeds from long-term debt	0	197,061,000	98,266,000
Repayment of long-term debt	(32,417,000)	(202,873,000)	(171,000)
Cash paid for dividends	(49,991,000)	(50,017,000)	(50,134,000)
Repurchase of shares in connection with stock repurchase program	0	(21,315,000)	(24,569,000)
Net cash provided by financing activities	167,639,000	1,762,106,000	1,401,579,000
Net (decrease) increase in cash and cash equivalents	(1,301,973,000)	1,244,762,000	218,273,000
Cash and cash equivalents at beginning of year	1,877,965,000	633,203,000	414,930,000
Cash and cash equivalents at end of year	575,992,000	1,877,965,000	633,203,000
Supplemental disclosures
Cash paid for interest	54,562,000	45,745,000	73,686,000
Cash paid for income taxes	41,764,000	50,977,000	39,989,000
Noncash transactions:
Transfers of loans to other real estate	2,207,000	3,180,000	8,588,000
Financed sales of other real estate owned	0	577,000	148,000
Recognition of operating right-of-use assets	3,475,000	8,142,000	9,393,000
Recognition of operating lease liabilities	3,475,000	8,142,000	9,393,000
Available for sale securities transferred to held to maturity securities	$ 882,927,000	$ 366,886,000	$ 0