Stockholders' Equity (Line Items in Consolidated Income Statements Affected by Amounts Reclassified from Accumulated Other Comprehensive Income) (Details) - Reclassification out of Accumulated Other Comprehensive Income [Member] - USD ($) $ in Thousands		3 Months Ended
		Mar. 31, 2021	Mar. 31, 2020
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Total reclassifications, net of tax	[1]	$ (1,183)	$ (134)
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]	56	195
Tax effect	[1]	(13)	(44)
Net of tax	[1]	43	151
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]	(1,954)	(1,232)
Tax effect	[1]	439	279
Net of tax	[1]	(1,515)	(953)
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]	6,136	1,569
Tax effect	[1]	(1,379)	(355)
Net of tax	[1]	4,757	1,214
Amortization of loss on terminated cash flow hedges	[1]		(705)
Tax effect	[1]		159
Net of tax	[1]		$ (546)
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 10 – Retirement Plans for additional details).