Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
CASH FLOWS FROM OPERATING ACTIVITIES:
Net income	$ 392,602	$ 524,089	$ 463,215
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	34,720	31,582	29,113
Provision for credit losses	59,103	(28,399)	(77,494)
Gain on other real estate and foreclosed assets	(967)	(4,382)	(2,280)
Deferred tax expense (benefit)	13,986	(22,166)	10,376
Increase in cash surrender value of life insurance contracts	(17,671)	(7,010)	(23,505)
(Gain) loss on disposal or impairment of assets	(15,753)	259	14,354
Loss on extinguishment of debt			4,165
Loss (gain) on sale of securities available for sale	65,380	87	(333)
Net (increase) decrease in loans held for sale	(24,589)	61,031	41,157
Net amortization of securities premium/discount	16,383	35,490	50,311
Amortization of intangible assets	11,556	14,033	16,665
Stock-based compensation expense	24,652	23,489	22,442
Net change in derivative collateral liability	58,326	64,867	62,670
Increase in interest payable and other liabilities	48,714	6,838	20,869
(Increase) decrease in other assets	(160,890)	176,354	(21,050)
Other, net	(10,303)	(34,141)	(24,985)
Net cash provided by operating activities	495,249	842,021	585,690
CASH FLOWS FROM INVESTING ACTIVITIES:
Proceeds from sales of securities available for sale	977,114	73,219	198,681
Proceeds from maturities of securities available for sale	813,214	502,628	1,073,133
Purchases of securities available for sale	(1,044,988)	(635,593)	(2,527,272)
Proceeds from maturities of securities held to maturity	163,266	147,879	116,536
Purchases of securities held to maturity	(6,023)	(884,427)	(338,089)
Proceeds received upon termination of fair value hedge instruments	19,275	90,601
Net redemptions (purchases) of Federal Home Loan Bank stock	(68,057)	(12,095)	52,535
Net (increase) decrease in short-term investments	(303,022)	3,506,845	(2,496,849)
Proceeds from sales of loans and leases	115,119	30,652	22,485
Net (increase) decrease in loans	(968,237)	(2,088,836)	670,958
Purchases of life insurance contracts	0	(65,000)	(75,000)
Proceeds from surrender of life insurance contracts	0	0	44,045
Purchases of property and equipment	(25,025)	(29,145)	(23,541)
Proceeds from sales of property	33,130	62	1,906
Proceeds from sales of other real estate and foreclosed assets	3,575	14,081	15,527
Other, net	(4,552)	11,487	40,361
Net cash provided by (used in) investing activities	(295,211)	662,358	(3,224,584)
CASH FLOWS FROM FINANCING ACTIVITIES:
Net increase (decrease) in deposits	619,710	(1,395,548)	2,768,020
Net increase (decrease) in short-term borrowings	(716,442)	206,210	(2,452)
Repayments of long-term debt	0	(480)	(153,444)
Issuance of long-term debt, net of issuance costs	0	5,629	22,388
Dividends paid	(104,697)	(94,458)	(95,927)
Payroll tax remitted on net share settlement of equity awards	(5,681)	(7,386)	(7,364)
Other repurchases of common stock	0	(58,892)	(21,796)
Proceeds from exercise of stock options	0	227	492
Proceeds from dividend reinvestment and stock purchase plan	3,815	3,577	3,872
Net cash provided by (used in) financing activities	(203,295)	(1,341,121)	2,513,789
NET INCREASE (DECREASE) IN CASH AND DUE FROM BANKS	(3,257)	163,258	(125,105)
CASH AND DUE FROM BANKS, BEGINNING	564,459	401,201	526,306
CASH AND DUE FROM BANKS, ENDING	561,202	564,459	401,201
SUPPLEMENTAL INFORMATION
Income taxes paid	103,190	135,193	122,594
Interest paid	487,681	80,076	49,995
SUPPLEMENTAL INFORMATION FOR NON-CASH INVESTING AND FINANCING ACTIVITIES
Assets acquired in settlement of loans	$ 4,302	$ 596	$ 2,806