Stockholders' Equity (Line Items in Consolidated Income Statements Affected by Amounts Reclassified from Accumulated Other Comprehensive Income) (Details) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Amortization of defined benefit pension and post-retirement items		$ 2,398	$ (45,198)	$ 17,315
Employee Benefit Plans [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Amortization of defined benefit pension and post-retirement items		2,398	(45,198)	$ 17,315
Amount Reclassified from Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Total reclassifications, net of tax	[1]	(12,833)	(30,468)
Amount Reclassified from 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 loss on securities transferred to HTM	[1]	(3,153)	(3,296)
Tax effect	[1]	713	755
Net of tax	[1]	(2,440)	(2,541)
Amount Reclassified from Accumulated Other Comprehensive Income [Member] | Available for Sale Securities [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Gain (loss) on sale of AFS securities	[1]		(25,480)
Tax effect	[1]		5,720
Net of tax	[1]		(19,760)
Amount Reclassified from 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]	(9,174)	(4,989)
Tax effect	[1]	2,074	1,122
Net of tax	[1]	(7,100)	(3,867)
Amount Reclassified from 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 (loss) on cash flow hedges	[1]	(110)	1,072
Tax effect	[1]	25	(244)
Net of tax	[1]	(85)	828
Amortization of loss on terminated cash flow hedges	[1]	(4,145)	(5,569)
Tax effect	[1]	937	1,269
Net of tax	[1]	$ (3,208)	$ (4,300)

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