Accumulated Other Comprehensive Income Changes in Other Comprehensive Income (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Equity [Abstract]
Unrealized gain on securities, before tax amount	$ 22,380	$ 26,062
Unrealized gain on securities, tax effect	(4,949)	(5,764)
Unrealized gain on securities, net of tax amount	17,431	20,298
Reclassification adjustment for securities gains included in net income, before tax amount	(46)	(65)
Reclassification adjustment for securities gains included in net income, tax effect	10	14
Reclassification adjustment for securities gains included in net income, net of tax amount	(36)	(51)
Other Comprehensive Income (Loss), Reclassification Adjustment From AOCI For Amortization Of Unrealized Losses On Investments Transferred From Available-For-Sale To Held-To-Maturity, Before Tax	1,022	1,252
Other Comprehensive Income (Loss), Reclassification Adjustment From AOCI For Amortization Of Unrealized Losses On Investments Transferred From Available-For-Sale To Held-To-Maturity, Tax	(227)	(278)
Other Comprehensive Income (Loss), Reclassification Adjustment From AOCI For Amortization Of Unrealized Losses On Investments Transferred From Available-For-Sale To Held-To Maturity, After Tax	795	974
Non-credit related unrealized gains on other-than-temporarily impaired debt securities, before tax amount		(105)
Non-credit related unrealized gains on other-than-temporarily impaired debt securities, tax effect		23
Non-credit related unrealized gains on other-than-temporarily impaired debt securities, net of tax amount	0	(82)
Amortization of net unrecognized pension and postretirement items, before tax amount	328	374
Amortization of net unrecognized pension and postretirement items, tax effect	(73)	(83)
Amortization of net unrecognized pension and postretirement items, net of tax amount	255	291
Total Other Comprehensive Income, Before Tax Amount	23,684	27,518
Total Other Comprehensive Income, Tax Effect	(5,239)	(6,088)
Other Comprehensive Income	$ 18,445	$ 21,430