Stockholders' Equity (Line Items in Consolidated Income Statements Affected by Amounts Reclassified from Accumulated Other Comprehensive Income) (Details) - USD ($) $ in Thousands		6 Months Ended
		Jun. 30, 2021	Jun. 30, 2020
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Amortization of defined benefit pension and post-retirement items			$ (10,251)
Employee Benefit Plans [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Amortization of defined benefit pension and post-retirement items			(10,251)
Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Total reclassifications, net of tax	[1]	$ 1,332	2,171
Reclassification out of Accumulated Other Comprehensive Income [Member] | Accumulated Other Comprehensive Loss Available for Sale Securities [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Loss on sale of AFS securities	[1]	(2,166)
Tax effect	[1]	487
Net of tax	[1]	(1,679)
Reclassification out of Accumulated Other Comprehensive Income [Member] | Held to Maturity Securities Transferred from AFS [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Amortization of unrealized net gain or loss or gain on securities transferred to HTM	[1]	101	289
Tax effect	[1]	(23)	(65)
Net of tax	[1]	78	224
Reclassification out of Accumulated Other Comprehensive Income [Member] | Employee Benefit Plans [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Amortization of defined benefit pension and post-retirement items	[1],[2]	(3,445)	(2,944)
Tax effect	[1]	774	666
Net of tax	[1]	(2,671)	(2,278)
Reclassification out of Accumulated Other Comprehensive Income [Member] | Gains and Losses on Cash Flow Hedges [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Reclassification of unrealized gain on cash flow hedges	[1]	12,991	6,550
Tax effect	[1]	(2,919)	(1,482)
Net of tax	[1]	10,072	5,068
Amortization of loss on terminated cash flow hedges	[1]		(1,089)
Tax effect	[1]		246
Net of tax	[1]		$ (843)
Reclassification out of Accumulated Other Comprehensive Income [Member] | Gains and Losses on Equity Method Investment [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Reclassification of unrealized loss on equity method investment	[1]	(4,468)
Net of tax	[1]	$ (4,468)

[1] Amounts in parentheses indicate reduction in net income.

[2] These AOCI components are included in the computation of net periodic pension and post-retirement cost that is reported with other noninterest expense (see Note 11 – Retirement Plans for additional details).