Consolidated Statements of Cash Flows - USD ($) $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2022	Mar. 31, 2021	Dec. 31, 2021
Cash Flow From Operating Activities
Net income	$ 74,262	$ 94,301
Adjustments to reconcile net income to net cash provided by (used in) operating activities
Provision for credit losses	(3,990)	(23,004)
Depreciation and amortization	11,680	12,038
Change in MSRs valuation(a)	(9,451)	(10,578)
Amortization of other intangible assets	2,203	2,236
Amortization and accretion on earning assets, funding, and other, net	5,338	7,941
Net amortization of tax credit investments	8,535	8,301
Losses (gains) on sales of investment securities, net	(21)	39
Asset (gains), net	(188)	(4,809)
(Gains) on sale of branch, net	0	(1,002)
(Gain) loss on mortgage banking activities, net	4,183	(10,326)
Mortgage loans originated and acquired for sale	(252,113)	(412,645)
Proceeds from sales of mortgage loans held for sale	296,089	400,135
Changes in certain assets and liabilities
(Increase) decrease in interest receivable	(2,592)	3,797
(Decrease) in interest payable	(1,917)	(8,694)
(Decrease) in expense payable	(46,737)	(12,818)
(Increase) decrease in net derivative position	152,545	69,829
Net change in other assets and other liabilities	8,292	43,027
Net cash provided by operating activities	246,119	157,768
Cash Flow From Investing Activities
Net decrease (increase) in loans	(305,878)	274,733
Purchases of
AFS securities	(409,376)	(809,140)
HTM securities	(135,301)	(37,215)
Federal Home Loan Bank and Federal Reserve Bank stocks and equity securities	(1)	(1)
Premises, equipment, and software, net of disposals	(17,141)	(6,477)
Proceeds from
Sales of AFS and equity securities	742	51,295
Prepayments, calls, and maturities of AFS securities	167,986	419,235
Prepayments, calls, and maturities of HTM securities	51,206	97,196
Sales, prepayments, calls, and maturities of other assets	18,012	8,525
Net change in tax credit and alternative investments	(10,293)	(12,990)
Net cash (used in) investing activities	(640,045)	(12,354)
Cash Flow From Financing Activities
Net increase (decrease) in deposits	(60,949)	1,225,867
Net decrease in deposits due to branch sales	0	(31,083)
Net increase (decrease) in short-term funding	45,098	(62,639)
Net increase in short-term FHLB advances	320,000	0
Repayment of long-term FHLB advances	(414,578)	(2,954)
Proceeds from long-term FHLB advances	11,506	251
(Repayment) proceeds of finance lease principal	399	(37)
Proceeds from issuance of common stock for stock-based compensation plans	6,654	10,556
Cash dividends on common stock	(30,583)	(27,870)
Cash dividends on preferred stock	(2,875)	(5,207)
Net cash provided by (used in) financing activities	(130,521)	1,085,319
Net increase (decrease) in cash and cash equivalents	(524,447)	1,230,732
Cash and cash equivalents at beginning of period	1,025,515	716,048	$ 716,048
Cash and cash equivalents at end of period(b)	501,068	1,946,780	1,025,515
Supplemental disclosures of cash flow information
Cash paid for interest	16,267	29,258
Cash (received from) income and franchise taxes	(1,471)	(114)
Loans and bank premises transferred to OREO	426	15,426
Capitalized mortgage servicing rights	3,042	3,348
Loans transferred into held for sale from portfolio, net	2,644	5,582
Transfer of AFS securities to HTM securities, Fair Value	1,621,990	0
Unsettled trades to purchase securities	4,246	3,000
Restricted Cash and Cash Equivalents
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents, Total	501,068	1,946,780	$ 1,025,515
Retained Earnings
Cash Flow From Operating Activities
Net income	74,262	94,301
ABRC
Proceeds from
Sales, prepayments, calls, and maturities of other assets		2,484
Whitnell
Proceeds from
Sales, prepayments, calls, and maturities of other assets	0
Performance/Service Based RSAs, RSA,
Cash Flow From Financing Activities
Payments for Repurchase of Common Stock	(5,193)	(3,593)
Board Authorized Purchase Program [Member]
Cash Flow From Financing Activities
Payments for Repurchase of Common Stock	$ 0	$ (17,973)