CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Accretion (Amortization) of Discounts and Premiums, Investments	$ (38,051)	$ (20,294)	$ (19,141)
Depreciation, amortization and accretion	45,203	8,342	(23,604)
Provision for credit losses	191,734	27,283	34,377
Gains on mortgage loans sold, net	60,042	24,335	14,564
Gain (Loss) on Sale of Investments	986	(5,941)	(2,254)
Stock-based compensation expense	18,737	21,226	17,636
Deferred Income Tax Expense (Benefit)	(58,315)	14,696	11,765
Gains Losses On Sales Of Other Real Estate And Other Investments	(7,604)	(2,927)	(84)
Income (Loss) from Equity Method Investments	83,539	90,111	51,222
Dividends received from equity method investment	53,020	51,312	33,651
Excess Tax Benefit from Share-based Compensation, Operating Activities	417	1,011	2,966
Gains on other loans sold, net	2,620	3,624	3,287
Increase (Decrease) in Other Operating Assets	157,294	57,499	24,471
Increase in other liabilities	81,322	79,264	60,617
Net cash provided by operating activities	427,825	434,288	470,757
Payments to Acquire Available-for-sale Securities	1,412,210	1,455,073	1,314,721
Proceeds from Sale of Available-for-sale Securities	145,631	737,717	169,850
Proceeds from Maturities, Prepayments and Calls of Debt Securities, Available-for-sale	469,337	372,300	323,571
Payments to Acquire Held-to-maturity Securities	0	3,822	0
Proceeds from Maturities, Prepayments and Calls of Held-to-maturity Securities	20,473	8,300	5,775
Payments for (Proceeds from) Loans and Leases	2,661,316	1,927,811	1,995,424
Payments to Acquire Property, Plant, and Equipment	38,761	42,153	23,739
Payment to Acquire Life Insurance Policy, Investing Activities	75,000	110,000	100,000
Proceeds from Insurance Settlement, Investing Activities	6,486	321	3,467
Proceeds from sales of software, premises, and equipment	0	66	2,967
Acquisitions, net of cash acquired	0	44,594	0
Proceeds from Sale of Other Real Estate	13,272	8,446	16,088
Proceeds from (payments for) derivative instruments	35,680		0
Payments for (Proceeds from) Derivative Instrument, Investing Activities		106,832
Payments to Acquire Intangible Assets	1,000	0	0
Payments for (Proceeds from) Other Investing Activities	71,254	55,926	56,918
Net cash used in investing activities	(3,568,662)	(2,619,061)	(2,969,084)
Net increase in deposits	7,524,867	1,332,491	2,399,407
Net increase (decrease) in repurchase agreements	1,810	21,613	(30,521)
Advances from Federal Home Loan Bank: Issuances	762,473	2,672,500	1,664,906
Payments of FHLBank Borrowings, Financing Activities	1,737,521	2,053,555	1,541,212
Proceeds from subordinated debt and other borrowings, net of issuance costs	56,568	316,078	19,850
Repayments of other borrowings	136,661	184,175	620
Repayments of Debt and Capital Lease Obligations	243	226	168
Proceeds from Issuance of Preferred Stock, Preference Stock, and Warrants	217,126	0	0
Issuance of common stock pursuant to restricted stock unit agreement, net of shares withheld for taxes	(2,488)	0	0
Exercise of common stock options, net of shares surrendered for taxes	2,577	3,694	5,071
Payments for Repurchase of Common Stock	50,790	61,416	20,694
Common dividends paid	49,389	49,828	45,454
Preferred stock dividends paid	7,596	0	0
Net cash provided by financing activities	6,575,579	1,989,788	2,440,423
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents, Period Increase (Decrease), Including Exchange Rate Effect	3,434,742	(194,985)	(57,904)
Cash, cash equivalents and restricted cash, beginning of year	526,707	721,692	779,596
Cash, cash equivalents and restricted cash, end of year	3,961,449	526,707	721,692
Commercial Loan [Member]
Payments for Origination and Purchases of Loans Held-for-sale	407,578	402,623	356,597
Proceeds from Sale of Loans Held-for-sale	396,584	404,615	369,387
Consumer Loan [Member]
Payments for Origination and Purchases of Loans Held-for-sale	2,122,796	1,396,968	1,195,435
Proceeds from Sale of Loans Held-for-sale	$ 2,176,836	$ 1,373,678	$ 1,234,551