Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Operating Activities
Net Income	$ 225,913	$ 219,602	$ 184,672
Adjustments to Reconcile Net Income to Net Cash Provided by Operating Activities:
Provision for Credit Losses	16,000	13,425	16,900
Depreciation and Amortization	17,268	14,389	13,048
Amortization of Deferred Loan and Lease Fees	476	(372)	(1,031)
Amortization and Accretion of Premiums/Discounts on Investment Securities, Net	20,683	32,966	39,186
Amortization of Operating Lease Right-of-Use-Assets	12,616	0	0
Share-Based Compensation	8,337	8,146	7,369
Benefit Plan Contributions	(1,926)	(1,749)	(11,454)
Deferred Income Taxes	(15,415)	(6,274)	4,177
Gain (Loss) on Disposition of Property Plant Equipment	(558)	0	0
Net Gains (Losses) on Sale of Loans and Leases	(10,357)	(3,834)	(6,780)
Net Losses (Gains) on Investment Securities	3,986	3,938	(10,430)
Proceeds from Sales of Loans Held for Sale	487,436	275,943	323,784
Originations of Loans Held for Sale	(510,909)	(267,066)	(326,195)
Net Tax Benefits from Share-Based Compensation	(727)	(993)	(2,521)
Net Change in Other Assets and Other Liabilities	(20,039)	27,815	(60,622)
Net Cash Provided by Operating Activities	234,238	317,922	175,145
Investment Securities Available-for-Sale:
Proceeds from Prepayments and Maturities	1,873,700	358,244	365,239
Purchases	(1,456,901)	(166,915)	(427,061)
Investment Securities Held-to-Maturity:
Proceeds from Prepayments and Maturities	794,157	853,635	882,748
Purchases	(1,380,430)	(419,640)	(995,076)
Net Change in Loans and Leases	(550,533)	(664,692)	(954,984)
Proceeds from Sale of Loans and Leases Held-for-investment	0	0	137,717
Premises and Equipment, Net	(53,900)	(35,300)	(30,470)
Proceeds from Sale of Premises and Equipment	639	0	0
Net Cash Used in Investing Activities	(773,268)	(74,668)	(1,021,887)
Financing Activities
Net Change in Deposits	757,241	143,273	563,728
Net Change in Short-Term Borrowings	99,811	(798)	(27,701)
Proceeds from Long-Term Debt	0	50,000	0
Repayments of Other Debt	(50,078)	(175,000)	0
Proceeds from Issuance of Common Stock	7,872	7,873	13,101
Repurchase of Common Stock	(137,649)	(91,988)	(47,076)
Cash Dividends Paid	(105,478)	(98,496)	(87,066)
Net Cash Provided by (Used in) Financing Activities	571,719	(165,136)	414,986
Net Change in Cash and Cash Equivalents	32,689	78,118	(431,756)
Cash and Cash Equivalents at Beginning of Period	558,658	525,969	447,851
Cash and Cash Equivalents at End of Period	525,969	447,851	879,607
Supplemental Information
Cash Paid for Interest	89,894	62,515	44,945
Cash Paid for Income Taxes	58,152	42,475	67,883
Operating lease right-of-use assets	100,838	0	0
Operating lease liabilities	108,210	0	0
Non-Cash Investing and Financing Activities:
Transfer from Loans to Foreclosed Real Estate	2,070	2,693	2,559
Transfers from Loans to Loans Held for Sale	$ 0	$ 0	$ 86,625