Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Operating Activities
Net Income	$ 54,040	$ 51,176
Adjustments to Reconcile Net Income to Net Cash Provided by Operating Activities:
Provision for Credit Losses	4,125	4,400
Depreciation and Amortization	3,339	3,280
Amortization of Deferred Loan and Lease Fees	(151)	(427)
Amortization and Accretion of Premiums/Discounts on Investment Securities, Net	8,966	10,130
Share-Based Compensation	1,867	1,735
Benefit Plan Contributions	(375)	(334)
Deferred Income Taxes	(138)	9,161
Net Gains on Sales of Loans and Leases	(573)	(2,168)
Net Losses (Gains) on Sales of Investment Securities	666	(12,133)
Proceeds from Sales of Loans Held for Sale	66,003	68,884
Originations of Loans Held for Sale	(70,290)	(73,983)
Net Tax Benefit from Share-Based Compensation	767	1,900
Net Change in Other Assets and Other Liabilities	6,632	(19,942)
Net Cash Provided by Operating Activities	74,878	41,679
Investment Securities Available-for-Sale:
Proceeds from Sales, Prepayments and Maturities	89,399	94,028
Purchases	(59,160)	(234,979)
Investment Securities Held-to-Maturity:
Proceeds from Prepayments and Maturities	195,199	161,465
Purchases	(59,598)	(181,048)
Net Change in Loans and Leases	(124,225)	(198,531)
Proceeds from Sales of Loans	0	79,169
Premises and Equipment, Net	(9,614)	(4,640)
Net Cash Provided by (Used in) Investing Activities	32,001	(284,536)
Financing Activities
Net Change in Deposits	73,165	156,293
Net Change in Short-Term Borrowings	0	(23,086)
Repayments of Long-Term Debt	(25,000)	0
Proceeds from Issuance of Common Stock	1,959	6,494
Repurchase of Common Stock	(17,541)	(11,509)
Cash Dividends Paid	(22,087)	(21,419)
Net Cash Provided by Financing Activities	10,496	106,773
Net Change in Cash and Cash Equivalents	117,375	(136,084)
Cash and Cash Equivalents at End of Period	565,226	743,523
Cash and Cash Equivalents at Beginning of Period	447,851	879,607
Supplemental Information
Cash Paid for Interest	11,908	8,905
Cash Paid for Income Taxes	961	1,822
Non-Cash Investing Activities:
Transfer from Loans to Foreclosed Real Estate	1,728	843
Transfers from Loans to Loans Held for Sale	$ 0	$ 30,477