Accumulated Other Comprehensive Income Changes in Other Comprehensive Income (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Equity [Abstract]
Unrealized gain on securities, before tax amount	$ 6,575	$ 26,193
Unrealized gain on securities, tax effect	(2,302)	(9,167)
Unrealized gain on securities, net of tax amount	4,273	17,026
Reclassification adjustment for securities gains included in net income, before tax amount	(1,106)	(947)
Reclassification adjustment for securities gains included in net income, tax effect	387	331
Reclassification adjustment for securities gains included in net income, net of tax amount	(719)	(616)
Amortization of unrealized loss on derivative financial instruments, before tax amount		6
Amortization of unrealized loss on derivative financial instruments, tax effect		(2)
Amortization of unrealized loss on derivative financial instruments, net of tax amount	0	4
Amortization of net unrecognized pension and postretirement items, before tax amount	528	717
Amortization of net unrecognized pension and postretirement items, tax effect	(185)	(251)
Amortization of net unrecognized pension and postretirement items, net of tax amount	343	466
Total Other Comprehensive Income, Before Tax Amount	5,997	25,969
Total Other Comprehensive Income, Tax Effect	(2,100)	(9,089)
Other Comprehensive Income	$ 3,897	$ 16,880