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 - USD ($) $ in Thousands		3 Months Ended
		Mar. 31, 2020	Mar. 31, 2019
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Total reclassifications, net of tax	[1]	$ (134)	$ (3,722)
Held to Maturity Securities Transferred from AFS [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Amortization of unrealized net loss or gain on securities transferred to HTM	[1]	195	(591)
Tax effect	[1]	(44)	134
Net of tax	[1]	151	(457)
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]	(1,232)	(2,203)
Tax effect	[1]	279	498
Net of tax	[1]	(953)	(1,705)
Gains and Losses on Cash Flow Hedges [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Reclassification of unrealized gain (loss) on cash flow hedges	[1]	1,569	(610)
Tax effect	[1]	(355)	138
Net of tax	[1]	1,214	(472)
Amortization of loss on terminated cash flow hedges	[1]	(705)	(1,406)
Tax effect	[1]	159	318
Net of tax	[1]	$ (546)	$ (1,088)

[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 employee benefits expense (see Note 11 – Retirement Plans for additional details).