Accumulated Other Comprehensive Loss (Components of Comprehensive Income) (Details) - USD ($) $ in Thousands	3 Months Ended						9 Months Ended		12 Months Ended
	Sep. 30, 2021	Jun. 30, 2021	Mar. 31, 2021	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020
Net unrealized gains (losses), before tax	$ (361)			$ 2,221			$ 179	$ 156
Net unrealized tax (expense) benefit	97			(589)			(48)	(36)
Other comprehensive (loss)/income, net of tax	(264)	$ 4,730	$ (4,335)	1,632	$ 4,120	$ (5,632)	131	120
Accumulated Other Comprehensive Loss [Member]
Unrealized net gains (losses), net of tax	(586)	4,519	(4,670)						$ (4,052)
Recognized gains (losses), net of tax	(322)	(211)	(335)						(1,160)
Other comprehensive (loss)/income, net of tax	(264)	4,730	(4,335)	1,632	$ 4,120	$ (5,632)
Investment securities- with OTTI [Member]
Unrealized net gains (losses), before tax	751			708			3,274	(1,249)
Net unrealized gains (losses), before tax	701			658			3,123	(1,400)
Unrealized tax (expense) benefit	(201)			(190)			(877)	335
Net unrealized tax (expense) benefit	(188)			(177)			(837)	375
Unrealized net gains (losses), net of tax	550	1,581	266	518			2,397	(914)	(587)
Recognized gains (losses), net of tax	37	37	37						148
Other comprehensive (loss)/income, net of tax	513			481			2,286	(1,025)
Investment securities- with OTTI [Member] | Accretable Yield in Income [Member]
Recognized gains (losses), before tax	50			50			151	151
Recognized tax (expense) benefit	(13)			(13)			(40)	(40)
Recognized gains (losses), net of tax	37			37			111	111
Investment securities- all other [Member]
Unrealized net gains (losses), before tax	(708)			(321)			(5,035)	2,446
Net unrealized gains (losses), before tax	(708)			(896)			(5,189)	1,824
Unrealized tax (expense) benefit	190			86			1,349	(655)
Net unrealized tax (expense) benefit	190			240			1,390	(488)
Unrealized net gains (losses), net of tax	(518)	2,034	(5,202)	(235)			(3,686)	1,791	1,291
Recognized gains (losses), net of tax		113							463
Other comprehensive (loss)/income, net of tax	(518)			(656)			(3,799)	1,336
Investment securities- all other [Member] | Recognition of Gains (Losses) In Income [Member]
Recognized gains (losses), before tax				575			154	622
Recognized tax (expense) benefit				(154)			(41)	(167)
Recognized gains (losses), net of tax				421			113	455
Investment securities HTM [Member]
Net unrealized gains (losses), before tax	42			74			150	749
Net unrealized tax (expense) benefit	(11)			(20)			(40)	(201)
Recognized gains (losses), net of tax	(31)	(34)	(45)						(584)
Other comprehensive (loss)/income, net of tax	31			54			110	548
Investment securities HTM [Member] | Recognition of Gains (Losses) In Income [Member]
Recognized gains (losses), before tax	(54)						(54)	60
Recognized tax (expense) benefit	14						14	(16)
Recognized gains (losses), net of tax	(40)						(40)	44
Investment securities HTM [Member] | Amortization of Recognized Income [Member]
Recognized gains (losses), before tax	12			(74)			(96)	(809)
Recognized tax (expense) benefit	(3)			20			26	217
Recognized gains (losses), net of tax	9			(54)			(70)	(592)
Accumulated Gain (Loss), Net, Cash Flow Hedge, Parent [Member]
Unrealized net gains (losses), before tax							615
Net unrealized gains (losses), before tax	108			90				(1,335)
Unrealized tax (expense) benefit							(165)
Net unrealized tax (expense) benefit	(29)			(18)				363
Unrealized net gains (losses), net of tax	79	(34)	405						(869)
Other comprehensive (loss)/income, net of tax	79			72			450	(972)
Defined Benefit Plans Adjustments [Member] | Pension [Member]
Unrealized net gains (losses), before tax	(951)			1,891			139	(895)
Net unrealized gains (losses), before tax	(579)			2,249			1,255	179
Unrealized tax (expense) benefit	254			(506)			(37)	240
Net unrealized tax (expense) benefit	155			(602)			(336)	(48)
Unrealized net gains (losses), net of tax	(697)	938	(139)	1,385			102	(655)	(3,262)
Recognized gains (losses), net of tax	(273)	(272)	(272)						(1,049)
Other comprehensive (loss)/income, net of tax	(424)			1,647			919	131
Defined Benefit Plans Adjustments [Member] | SERP [Member]
Recognized gains (losses), before tax								139
Net unrealized gains (losses), before tax	75			46			225
Net unrealized tax (expense) benefit	(20)			(12)			(60)	(37)
Unrealized net gains (losses), net of tax									(625)
Recognized gains (losses), net of tax	(55)	$ (55)	$ (55)						$ (138)
Other comprehensive (loss)/income, net of tax	55			34			165	102
Defined Benefit Plans Adjustments [Member] | Amortization of Unrecognized Loss [Member] | Pension [Member]
Recognized gains (losses), before tax	(372)			(358)			(1,116)	(1,074)
Recognized tax (expense) benefit	99			96			299	288
Recognized gains (losses), net of tax	(273)			(262)			(817)	(786)
Defined Benefit Plans Adjustments [Member] | Amortization of Unrecognized Loss [Member] | SERP [Member]
Recognized gains (losses), before tax	(76)			(47)			(226)	(141)
Recognized tax (expense) benefit	20			13			60	38
Recognized gains (losses), net of tax	$ (56)			(34)			(166)	(103)
Defined Benefit Plans Adjustments [Member] | Amortization of Prior Service Costs [Member] | SERP [Member]
Recognized gains (losses), before tax				1			1	2
Recognized tax (expense) benefit				$ (1)				(1)
Recognized gains (losses), net of tax							$ 1	$ 1