Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
CASH FLOWS FROM OPERATING ACTIVITIES:
Net income (loss)	$ 463,215	$ (45,174)	$ 327,380
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	29,113	30,128	30,902
Provision for credit losses	(77,494)	602,904	47,708
(Gain) loss on other real estate and foreclosed assets	(2,280)	9,581	626
Deferred tax expense (benefit)	10,376	(20,716)	47,100
Increase in cash surrender value of life insurance contracts	(23,505)	(19,244)	(16,158)
Impairment of or loss on disposal of assets	14,354	3,159	1,109
Loss on extinguishment of debt	4,165
Gain on sale of securities available for sale	(333)	(488)
Gain on the sale of loans and leases	(1,208)	(1,203)	(619)
Net (increase) decrease in loans held for sale	41,157	(77,544)	(27,773)
Net amortization of securities premium/discount	50,311	43,226	32,166
Amortization of intangible assets	16,665	19,916	20,844
Stock-based compensation expense	22,442	21,107	20,902
Net change in liability from variation margin collateral	62,670	(80,290)	(21,326)
Contribution to pension plan			(100,000)
Increase in interest payable and other liabilities	20,869	4,687	19,573
Increase in other assets	(21,050)	(111,094)	(22,556)
Other, net	(23,777)	(23,764)	(7,929)
Net cash provided by operating activities	585,690	355,191	351,949
CASH FLOWS FROM INVESTING ACTIVITIES:
Proceeds from sales of securities available for sale	198,681	211,919	268,413
Proceeds from maturities of securities available for sale	1,073,133	1,001,720	294,681
Purchases of securities available for sale	(2,527,272)	(2,371,954)	(1,010,805)
Proceeds from maturities of securities held to maturity	116,536	218,205	417,520
Purchases of securities held to maturity	(338,089)	(20,884)	(183,626)
Net redemptions (purchases) of Federal Home Loan Bank stock	52,535	(12,868)	(35,151)
Net (increase) decrease in short-term investments	(2,496,849)	(1,223,557)	281,251
Proceeds from sale of loans and leases	22,485	328,958	112,048
Net (increase) decrease in loans	670,958	(1,296,136)	(555,008)
Purchases of life insurance contracts	(75,000)		(32,788)
Proceeds from surrender of life insurance contracts	44,045
Purchases of property and equipment	(23,541)	(37,869)	(42,716)
Proceeds from sales of other real estate	15,527	17,923	30,658
Cash acquired in stock-based business combination			28,059
Consideration paid in business combination			(1,112)
Other, net	42,267	7,071	(30,446)
Net cash used in investing activities	(3,224,584)	(3,177,472)	(459,022)
CASH FLOWS FROM FINANCING ACTIVITIES:
Net increase (decrease) in deposits	2,768,020	3,894,302	(627,557)
Net increase (decrease) in short-term borrowings	(2,452)	(1,047,359)	1,058,748
Repayments of long-term debt	(153,444)	(308)	(14,222)
Issuance of long-term debt, net of issuance costs	22,388	166,425	20,846
Dividends paid	(95,927)	(95,605)	(94,871)
Payroll tax remitted on net share settlement of equity awards	(7,364)	(4,530)	(6,295)
Cash (received) paid under accelerated share repurchase agreement		12,110	(185,000)
Other repurchases of common stock	(21,796)	(12,716)
Proceeds from exercise of stock options	492		542
Proceeds from dividend reinvestment and stock purchase plan	3,872	4,164	3,614
Net cash provided by financing activities	2,513,789	2,916,483	155,805
NET INCREASE (DECREASE) IN CASH AND DUE FROM BANKS	(125,105)	94,202	48,732
CASH AND DUE FROM BANKS, BEGINNING	526,306	432,104	383,372
CASH AND DUE FROM BANKS, ENDING	401,201	526,306	432,104
SUPPLEMENTAL INFORMATION
Income taxes paid	122,594	17,465	28,288
Interest paid	49,995	121,343	232,456
SUPPLEMENTAL INFORMATION FOR NON-CASH INVESTING AND FINANCING ACTIVITIES
Assets acquired in settlement of loans	$ 2,806	$ 6,420	$ 21,285