Stockholders' Equity (Line Items in Consolidated Income Statements Affected by Amounts Reclassified from Accumulated Other Comprehensive Income) (Details) - Amount Reclassified from Accumulated Other Comprehensive Income [Member] - USD ($) $ in Thousands		6 Months Ended
		Jun. 30, 2019	Jun. 30, 2018
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Total reclassifications, net of tax	[1]	$ (7,495)	$ (4,403)
Held to Maturity Securities Transferred from AFS [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Amortization of unrealized net loss on securities transferred to HTM	[1]	(1,481)	(1,680)
Tax effect	[1]	335	380
Net of tax	[1]	(1,146)	(1,300)
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]	(4,527)	(2,448)
Tax effect	[1]	1,023	555
Net of tax	[1]	(3,504)	(1,893)
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]	(1,204)	979
Tax effect	[1]	272	(222)
Net of tax	[1]	(932)	757
Amortization of loss on terminated cash flow hedges	[1]	(2,472)	(2,544)
Tax effect	[1]	559	577
Net of tax	[1]	$ (1,913)	$ (1,967)

[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 12 – Retirement Plans for additional details).