Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Operating Activities
Net Income	$ 153,804	$ 225,913	$ 219,602
Adjustments to Reconcile Net Income to Net Cash Provided by Operating Activities:
Provision for Credit Losses	117,800	16,000	13,425
Depreciation and Amortization	20,205	17,268	14,389
Amortization of Deferred Loans and Leases (Fees) Costs, Net	(3,197)	476	(372)
Amortization and Accretion of Premiums/Discounts on Investment Securities, Net	27,586	20,683	32,966
Amortization of Operating Lease Right-of-Use-Assets	12,281	12,616
Share-Based Compensation	7,578	8,337	8,146
Benefit Plan Contributions	(1,615)	(1,926)	(1,749)
Deferred Income Taxes	(42,586)	(15,415)	(6,274)
Gains on Sale of Premises and Equipment	(1,850)	(558)
Impairment on Leveraged Lease	2,951
Impairment on ISB Closures and ATMs	4,168
Net Gains on Sales of Loans and Leases	(12,875)	(10,357)	(3,834)
Net (Gains) Losses on Investment Securities	(9,932)	3,986	3,938
Proceeds from Sales of Loans Held for Sale	394,196	487,436	275,943
Originations of Loans Held for Sale	(394,649)	(510,909)	(267,066)
Net Tax Benefits from Share-Based Compensation	485	727	993
Net Change in Other Assets and Other Liabilities	(127,934)	(20,039)	27,815
Net Cash Provided by Operating Activities	146,416	234,238	317,922
Investment Securities Available-for-Sale:
Proceeds from Sales, Prepayments and Maturities	1,003,432	1,873,700	358,244
Purchases	(2,114,912)	(1,456,901)	(166,915)
Investment Securities Held-to-Maturity:
Proceeds from Prepayments and Maturities	1,420,853	794,157	853,635
Purchases	(1,661,180)	(1,380,430)	(419,640)
Net Change in Loans and Leases	(990,169)	(550,533)	(664,692)
Premises and Equipment, Net	(33,287)	(53,900)	(35,300)
Proceeds from Sale of Premises and Equipment	1,981	639
Net Cash Used in Investing Activities	(2,373,282)	(773,268)	(74,668)
Financing Activities
Net Change in Deposits	2,427,147	757,241	143,273
Net Change in Short-Term Borrowings	(3,716)	99,811	(798)
Proceeds from Other Debt	50,000		50,000
Repayments of Other Debt	(75,084)	(50,078)	(175,000)
Proceeds from Issuance of Common Stock	9,389	7,872	7,873
Repurchase of Common Stock	(18,006)	(137,649)	(91,988)
Cash Dividends Paid	(107,434)	(105,478)	(98,496)
Net Cash Provided by (Used in) Financing Activities	2,282,296	571,719	(165,136)
Net Change in Cash and Cash Equivalents	55,430	32,689	78,118
Cash and Cash Equivalents at Beginning of Period	558,658	525,969	447,851
Cash and Cash Equivalents at End of Period	614,088	558,658	525,969
Supplemental Information
Cash Paid for Interest	53,026	89,894	62,515
Cash Paid for Income Taxes	60,182	58,152	42,475
Non-Cash Investing and Financing Activities:
Initial Recognition of Operating Lease Right-of-Use Assets		106,514
Initial Recognition of Operating Lease Liabilities		113,394
Transfer from Loans to Foreclosed Real Estate		$ 2,070	$ 2,693
Transfers from Loans to Loans Held for Sale	$ 32,423