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		3 Months Ended
		Mar. 31, 2018	Mar. 31, 2017
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Total reclassifications, net of tax	[1]	$ (1,972)	$ (1,267)
HTM 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]	(755)	(650)
Tax effect	[1]	171	266
Net of tax	[1]	(584)	(384)
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]	(1,177)	(1,387)
Tax effect	[1]	267	504
Net of tax	[1]	(910)	$ (883)
Cash Flow Hedges [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Reclassification of unrealized gain on cash flow hedges	[1]	336
Tax effect	[1]	(76)
Net of tax	[1]	260
Amortization of loss on terminated cash flash hedges	[1]	(954)
Tax effect	[1]	216
Net of tax	[1]	$ (738)

[1] Three Months EndedAmount reclassified from AOCI (a) March 31,Affected line item on(in thousands)20182017the statement of incomeAmortization of unrealized net loss on securities transferred to HTM (755) (650)Interest incomeTax effect 171 266Income taxesNet of tax (584) (384)Net incomeAmortization of defined benefit pension and post-retirement items (1,177) (1,387)Other noninterest expense (b)Tax effect 267 504Income taxesNet of tax (910) (883)Net incomeReclassification of unrealized gain on cash flow hedges 336 -Interest incomeTax effect (76) -Income taxesNet of tax 260Net incomeAmortization of loss on terminated cash flow hedges (954) -Interest incomeTax effect 216 -Income taxesNet of tax (738) -Net incomeTotal reclassifications, net of tax$ (1,972)$ (1,267)Net incomeAmounts in parenthesis 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).