Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Operating Activities:
Net income	$ 408,864	$ 220,621	$ 382,723
Adjustments to reconcile net income to net cash provided by operating activities:
(Benefit) provision for credit losses	(54,500)	137,750	37,800
Deferred tax expense (benefit)	(4,998)	(31,236)	927
Depreciation and amortization	35,913	36,616	37,507
Amortization of earning assets and funding premium/discount, net	133,069	75,929	49,731
Amortization of low-income housing tax credit investments	3,918	5,286	3,249
Amortization of mortgage servicing assets	5,593	6,562	7,318
Stock-based compensation	13,662	12,179	12,626
Gain on sale, net of write-down, on foreclosed and repossessed assets	(744)	(1,938)	(729)
Loss (gain) on sale, net of write-down, on premises and equipment	(1,236)	1,105	1,340
Net (gain) on sale of investment securities	0	(8)	(29)
Increase in cash surrender value of life insurance policies	(14,429)	(14,561)	(14,612)
Gain from life insurance policies	(4,402)	(1,219)	(4,933)
Net (gain) on mortgage banking activities	(5,912)	(15,305)	(4,031)
Net (gain) on sale of loans not originated for sale	(3,862)	(301)	(667)
Proceeds from sale of loans held for sale	247,634	486,341	216,239
Originations of loans held for sale	(235,066)	(449,803)	(240,305)
Net decrease (increase) in derivative contract assets net of liabilities	173,506	(118,336)	(123,752)
Net (increase) decrease in accrued interest receivable and other assets	(69,263)	11,120	(35,774)
Net (decrease) increase in accrued expenses and other liabilities	38,064	(8,121)	(23,257)
Net cash provided by operating activities	688,592	380,549	303,850
Investing Activities:
Purchases of available-for-sale securities	(1,957,562)	(990,904)	(549,541)
Proceeds from maturities and principal payments of available-for-sale securities	935,621	627,577	556,283
Proceeds from sales of available-for-sale securities	0	8,963	70,087
Purchases of held-to-maturity securities	(1,968,133)	(1,297,535)	(1,571,604)
Proceeds from maturities and principal payments of held-to-maturity securities	1,288,140	983,864	573,703
Net proceeds from (purchase of) Federal Home Loan Bank stock	5,758	71,452	240
Purchases of intercompany debt securities	(11,361)	(12,244)	(6,065)
Net (increase) in loans	(773,443)	(1,681,947)	(1,642,501)
Proceeds from loans not originated for sale	82,187	9,197	20,931
Proceeds from life insurance policies	5,074	1,885	12,866
Proceeds from the sale of foreclosed properties and repossessed assets	1,998	11,497	11,562
Proceeds from the sale of premises and equipment	3,221	866	0
Additions to premises and equipment	(16,589)	(21,280)	(25,717)
Net cash provided by (used for) investing activities	(2,405,089)	(2,288,609)	(2,549,756)
Financing Activities:
Net increase in deposits	2,511,163	4,006,319	1,465,377
Proceeds from Federal Home Loan Bank advances	180,470	3,850,000	9,200,000
Repayments of Federal Home Loan Bank advances	(302,637)	(5,665,312)	(9,078,332)
Net (decrease) increase in securities sold under agreements to repurchase and other borrowings	(320,459)	(45,076)	458,557
Proceeds from the issuance of long-term debt	0	0	300,000
Debt issuance costs	0	0	(3,642)
Dividends paid to common shareholders	(144,807)	(144,965)	(140,783)
Dividends paid to preferred shareholders	(7,875)	(7,875)	(7,875)
Exercise of stock options	3,492	240	619
Common stock repurchased	0	(76,556)	(13,003)
Common shares acquired related to stock compensation plan activity	(4,384)	(3,506)	(6,616)
Net cash (used for) provided by financing activities	1,914,963	1,913,269	2,174,302
Net (decrease) increase in cash and cash equivalents	198,466	5,209	(71,604)
Cash and cash equivalents at beginning of year	263,104	257,895	329,499
Cash and cash equivalents at end of year	461,570	263,104	257,895
Supplemental disclosure of cash flow information:
Interest paid	42,151	118,123	197,200
Income taxes paid	112,587	94,072	110,057
Noncash investing and financing activities:
Transfer of loans and leases to foreclosed properties and repossessed assets	1,757	5,394	10,440
Transfer of loans from portfolio to loans held for sale	78,316	8,578	16,609
Deposits assumed	0	4,657	0
Operating Lease, Right-of-Use Asset	119,926	127,481	157,234
Operating Lease, Liability	144,804	158,280	178,802
Increase (Decrease) in Leasing Receivables	$ (22,781)	$ (27,868)	$ (2,479)