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		$ 350,994	$ 306,771	$ 326,790
Adjustments to reconcile net income to net cash provided by operating activities:
Provision for credit losses		(88,011)	174,006	16,000
Depreciation and amortization		46,508	50,567	58,149
Addition to (recovery of) valuation allowance on mortgage servicing rights, net		(16,186)	17,704	63
Amortization of mortgage servicing rights		19,436	22,664	12,432
Amortization of other intangible assets		8,844	10,192	9,948
Amortization and accretion on earning assets, funding, and other, net		15,088	25,028	23,573
Net amortization of tax credit investments		34,070	25,556	20,062
Losses (gains) on sales of investment securities, net		16	(9,222)	(5,957)
Asset (gains) losses, net	[1]	(11,009)	(155,589)	(2,713)
(Gains) on sale of branches, net		(1,038)	(7,449)	0
(Gain) on mortgage banking activities, net		(39,106)	(59,379)	(20,120)
Mortgage loans originated for sale		(1,749,556)	(1,642,135)	(1,090,792)
Proceeds from sales of mortgage loans held for sale		1,774,791	1,959,571	1,317,077
Decrease in interest receivable		9,735	933	7,595
Increase (decrease) in interest payable		(10,675)	(11,385)	2,495
Increase (decrease) in accrued expenses		24,645	(29,057)	723
Increase (decrease) in derivative position		120,418	(113,760)	(102,966)
Increase (decrease) in net income tax position		(13,931)	(47,268)	43,908
Net change in other assets and other liabilities		54,520	32,270	(42,005)
Net cash provided by operating activities		529,551	550,020	574,260
Cash Flows from Investing Activities
Net decrease (increase) in loans		198,631	(1,640,524)	(137,990)
Purchases of
AFS securities		(2,746,994)	(1,648,938)	(460,124)
HTM securities		(622,485)	(125,480)	(423,682)
Federal Home Loan Bank and Federal Reserve Bank stocks		(10)	(84,152)	(246,836)
Premises, equipment, and software		(52,281)	(54,682)	(67,459)
Other intangibles		0	(200)	0
Proceeds from
Proceeds from sales of investment securities		158,743	626,283	1,367,476
Sale of Federal Home Loan Bank and Federal Reserve Bank stocks		0	144,000	270,023
Prepayments, calls, and maturities of AFS investment securities		1,216,657	1,343,056	561,659
Prepayments, calls, and maturities of HTM investment securities		299,761	449,078	260,510
Sales, prepayments, calls and maturities of other assets		29,833	27,964	10,250
Net change in tax credit and alternative investments		(68,455)	(55,134)	(67,632)
Net cash (paid) received in acquisitions		0	(31,518)	551,250
Net cash provided by (used in) investing activities		(1,584,186)	(793,737)	1,617,446
Cash Flows from Financing Activities
Net increase (decrease) in deposits		2,015,423	2,497,378	(1,842,748)
Net decrease in deposits due to branch sales		(31,083)	(222,878)	0
Net increase (decrease) in short-term funding		101,946	(238,655)	308,039
Net (decrease) in short-term FHLB advances		0	(520,000)	(380,000)
Repayment of long-term FHLB advances		(18,437)	(1,040,972)	(764,657)
Proceeds from long-term FHLB advances		6,950	4,215	751,573
Redemption of Corporation's senior notes		(300,000)	0	(250,000)
Repayment of finance lease principal		(965)	(1,081)	(1)
Proceeds from issuance of preferred stock		0	96,796	0
Proceeds from issuance of common stock for stock-based compensation plans		25,702	3,966	11,216
Redemption of preferred stock		(164,458)	0	0
Cash dividends on common stock		(116,061)	(112,023)	(111,804)
Cash dividends on preferred stock		(17,111)	(18,358)	(15,202)
Net cash provided by (used in) financing activities		1,364,102	371,020	(2,479,660)
Net increase (decrease) in cash and cash equivalents		309,467	127,304	(287,954)
Cash and cash equivalents at beginning of period		716,048	588,744	876,698
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents, Ending Balance		1,025,515	716,048	588,744
Restricted Cash		0	0	189,000
Supplemental disclosures of cash flow information
Cash paid for interest		81,604	159,291	332,919
Cash paid for income and franchise taxes		57,728	17,734	41,131
Loans and bank premises transferred to OREO		35,553	19,261	10,513
Capitalized mortgage servicing rights		16,151	13,667	11,606
Loans transferred into held for sale from portfolio, net		6,010	264,570	313,570
Transfer of HTM securities to AFS securities (adoption of ASU 2019-04)		0	0	692,414
Unsettled trades to purchase securities		4,459	0	0
Acquisitions
Fair value of assets acquired, including cash and cash equivalents		0	456,480	695,848
Fair value ascribed to goodwill and intangible assets		0	23,548	29,837
Fair value of liabilities assumed		0	480,028	725,764
Common stock issued in acquisition		0	0	(79)
ABRC [Member]
Proceeds from
Net cash received in sale of subsidiary		2,415	256,511	0
Performance/Service Based RSAs, RSA, [Member]
Cash Flows from Financing Activities
Payments for Repurchase of Common Stock		4,847	6,113	8,592
Board Authorized Purchase Program [Member]
Cash Flows from Financing Activities
Payments for Repurchase of Common Stock		$ 132,955	$ 71,255	$ 177,484

[1] The year ended December 31, 2020 includes a gain of $163 million from the sale of ABRC.(b) Includes the deposit premium on the sale of branches net of miscellaneous costs to sell. See Note 2 Acquisitions and Dispositions for additional details on the branch sales.