Stockholders' Equity (Line Items in Consolidated Income Statements Affected by Amounts Reclassified from Accumulated Other Comprehensive Income) (Details) - USD ($) $ in Thousands		9 Months Ended
		Sep. 30, 2020	Sep. 30, 2019
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Amortization of defined benefit pension and post-retirement items		$ (10,251)	$ (7,015)
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)	(7,015)
Reclassification out of Accumulated Other Comprehensive Income
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Total reclassifications, net of tax	[1]	5,394	(10,774)
Reclassification out of Accumulated Other Comprehensive Income | 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]	378	(2,435)
Tax effect	[1]	(85)	551
Net of tax	[1]	293	(1,884)
Reclassification out of Accumulated Other Comprehensive Income | 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]	(4,656)	(6,851)
Tax effect	[1]	1,053	1,546
Net of tax	[1]	(3,603)	(5,305)
Reclassification out of Accumulated Other Comprehensive Income | 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]	12,602	(1,200)
Tax effect	[1]	(2,851)	271
Net of tax	[1]	9,751	(929)
Amortization of loss on terminated cash flow hedges	[1]	(1,353)	(3,432)
Tax effect	[1]	306	776
Net of tax	[1]	$ (1,047)	$ (2,656)

[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 12 – Retirement Plans for additional details).