Accumulated Other Comprehensive Income Changes in Other Comprehensive Income (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Equity [Abstract]
Unrealized gain on securities, before tax amount	$ 26,062	$ (34,991)
Unrealized gain on securities, tax effect	(5,764)	7,347
Unrealized gain on securities, net of tax amount	20,298	(27,644)
Reclassification adjustment for securities gains included in net income, before tax amount	(65)	(19)
Reclassification adjustment for securities gains included in net income, tax effect	14	3
Reclassification adjustment for securities gains included in net income, net of tax amount	(51)	(16)
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	(1,252)
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	(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	(974)	0
Non-credit related unrealized gains on other-than-temporarily impaired debt securities, before tax amount	(105)	285
Non-credit related unrealized gains on other-than-temporarily impaired debt securities, tax effect	23	(61)
Non-credit related unrealized gains on other-than-temporarily impaired debt securities, net of tax amount	(82)	224
Amortization of net unrecognized pension and postretirement items, before tax amount	374	430
Amortization of net unrecognized pension and postretirement items, tax effect	(83)	(91)
Amortization of net unrecognized pension and postretirement items, net of tax amount	291	339
Total Other Comprehensive Income, Before Tax Amount	27,518	(34,295)
Total Other Comprehensive Income, Tax Effect	(6,088)	7,198
Other Comprehensive Income (Loss)	$ 21,430	$ (27,097)