Shareholders' Equity (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Before-Tax Amount
Unrealized loss on available for sale securities	$ (31,235)	$ 16,051	$ (22,907)
Reclassification adjustment for securities gains included in net income	(37)	(9,071)	(2,550)
Amortization of net unrealized losses on available for sale securities transferred to held to maturity	2,694
Non-credit related unrealized loss on other-than-temporarily impaired debt securities	285	285	(285)
Amortization of unrealized loss on derivative financial instruments			25
Unrecognized pension and postretirement income	1,798	(937)	(1,432)
Amortization of net unrecognized pension and postretirement income	2,116	2,092	1,869
Total Other Comprehensive Loss	(24,379)	8,420	(25,280)
Tax Effect
Unrealized loss on available for sale securities	6,909	(5,619)	8,016
Reclassification adjustment for securities gains included in net income	7	3,177	893
Amortization of net unrealized losses on available for sale securities transferred to held to maturity	(596)
Non-credit related unrealized loss on other-than-temporarily impaired debt securities	(63)	(100)	100
Amortization of unrealized loss on derivative financial instruments			(9)
Unrecognized pension and postretirement income	(398)	328	501
Amortization of net unrecognized pension and postretirement income	(468)	(731)	(653)
Total Other Comprehensive Loss	5,391	(2,945)	8,848
Net of Tax Amount
Unrealized loss on available for sale securities	(24,326)	10,432	(14,891)
Reclassification adjustment for securities gains included in net income	(30)	(5,894)	(1,657)
Non-credit related unrealized loss on other-than-temporarily impaired debt securities	222	185	(185)
Amortization of net unrealized losses on available for sale securities transferred to held to maturity	2,098
Amortization of unrealized loss on derivative financial instruments	0	0	16
Unrecognized pension and postretirement income	1,400	(609)	(931)
Amortization of net unrecognized pension and postretirement income	1,648	1,361	1,216
Total Other Comprehensive Loss	$ (18,988)	$ 5,475	$ (16,432)