Reconciliation of changes in the components of OCI (Details) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Other Comprehensive Income (Loss), Cash Flow Hedge, Gain (Loss), Reclassification, Tax		$ (281)	$ 180
Other Comprehensive Income (Loss), Cash Flow Hedge, Gain (Loss), before Reclassification, after Tax		5,548	182	$ 680
Other Comprehensive Income (Loss), Cash Flow Hedge, Gain (Loss), Reclassification, before Tax		1,000	(441)
Other Comprehensive Income (Loss), Cash Flow Hedge, Gain (Loss), Reclassification, after Tax		719	(261)
Other Comprehensive Income (Loss), Available-for-sale Securities, Tax, Portion Attributable to Parent		1,422	322	699
Other Comprehensive Income (Loss), Cash Flow Hedge, Gain (Loss), before Reclassification and Tax		7,717	307	1,133
Other Comprehensive Income (Loss), Cash Flow Hedge, Gain (Loss), before Reclassification, Tax		(2,169)	(125)	(453)
Other Comprehensive Income (Loss), Cash Flow Hedge, Gain (Loss), after Reclassification, before Tax		6,717	748
Other Comprehensive Income (Loss), Cash Flow Hedge, Gain (Loss), after Reclassification, Tax		1,888	305
Other Comprehensive Income (Loss), Cash Flow Hedge, Gain (Loss), after Reclassification and Tax		4,829	443	2,170
Other Comprehensive Income (Loss), before Tax [Abstract]
Change in fair value of securities available for sale, pre tax amount		5,923	996	1,858
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI on Borrowings Expense, before Tax	[1]			(2,520)
Other Comprehensive Income (Loss), Derivatives Qualifying as Hedges, before Tax, Portion Attributable to Parent				3,653
Other Comprehensive Income (Loss), Defined Benefit Plan, Gain (Loss) Arising During Period, before Tax		1,521	(995)	(383)
Other Comprehensive Income (Loss), Defined Benefit Plan, Gain (Loss), Reclassification Adjustment from AOCI, before Tax		372	278	238
Amortization of certain costs included in net periodic retirement costs, pre tax amount		(276)	(276)	(276)
Other Comprehensive (Income) Loss, Defined Benefit Plan, after Reclassification Adjustment, before Tax	[2]	2,169	(441)	131
Total other comprehensive loss, pre tax amount		2,963	(692)	1,952
Other Comprehensive Income (Loss), Tax [Abstract]
Other Comprehensive Income (Loss), Securities, Available-for-Sale, Unrealized Holding Gain (Loss) Arising During Period, Tax		1,422	321	710
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI on Borrowings Expense, Tax	[1]			1,030
Other Comprehensive Income (Loss), Derivatives Qualifying as Hedges, Tax, Portion Attributable to Parent				(1,483)
Other Comprehensive Income (Loss), Defined Benefit Plan, Gain (Loss) Arising During Period, Tax		(428)	407	157
Other Comprehensive Income (Loss), Defined Benefit Plan, Gain (Loss), Reclassification Adjustment from AOCI, Tax		(105)	(113)	(97)
Other Comprehensive (Income) Loss, Defined Benefit Plan, Prior Service Cost (Credit), Reclassification Adjustment from AOCI, Tax		(78)	(113)	(113)
Other Comprehensive (Income) Loss, Defined Benefit Plan, after Reclassification Adjustment, Tax	[2]	(611)	181	(53)
Other Comprehensive Income (Loss), Tax, Portion Attributable to Parent		(1,077)	198	(837)
Other Comprehensive Income (Loss), Net of Tax [Abstract]
Other Comprehensive Income (Loss), Securities, Available-for-Sale, Unrealized Holding Gain (Loss) Arising During Period, after Tax		(4,501)	(675)	(1,148)
Other Comprehensive Income (Loss), Available-for-sale Securities Adjustment, Net of Tax, Portion Attributable to Parent		(4,501)	(677)	(1,133)
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI on Borrowings Expense, Net of Tax	[1]			(1,490)
Other Comprehensive Income (Loss), Derivatives Qualifying as Hedges, Net of Tax, Portion Attributable to Parent				2,170
Other Comprehensive Income (Loss), Defined Benefit Plan, Gain (Loss) Arising During Period, after Tax		1,093	(588)	(226)
Other Comprehensive Income (Loss), Defined Benefit Plan, Gain (Loss), Reclassification Adjustment from AOCI, after Tax		267	165	141
Amortization of certain costs included in net periodic retirement costs, after tax amount		198	163	163
Other Comprehensive (Income) Loss, Defined Benefit Plan, after Reclassification Adjustment, after Tax	[2]	1,558	(260)	78
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent		1,886	(494)	1,115
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI for Sale of Securities, before Tax		0	3	(26)
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI for Sale of Securities, Tax		0	(1)	11
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI for Sale of Securities, Net of Tax		0	2	(15)
Other Comprehensive Income (Loss), Available-for-sale Securities Adjustment, before Tax, Portion Attributable to Parent		$ (5,923)	$ (999)	$ (1,832)

[1] Includes the amortization of the remaining balance of a realized but unrecognized gain, net of tax, from the termination of interest rate swaps in 2009. The original gain of $1.4 million, net of tax, was recognized in earnings through December 2018, the original maturity date of the swap. The balance of this gain was fully amortized into earnings at December 31, 2018. The balance of the gain was amortized to $137,000, and $281,000 at December 31, 2017 and 2016, respectively.

[2] The amortization of prior service costs is included in the computation of net periodic pension costs as disclosed in Note 15 - Employee Benefit Plans.