Shareholders' Equity (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Before-Tax Amount
Unrealized loss on securities	$ (11,872)	$ 51,901	$ (76,319)
Reclassification adjustment for securities gains included in net income (1)	(9,066)	(2,041)	(8,004)
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI on Derivatives, before Tax	3,778
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI on Derivatives, Tax	(1,322)
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI on Derivatives, Net of Tax	2,456	0	0
Non-credit related unrealized gains on other-than-temporarily impaired debt securities	368	1,200	3,042
Unrealized gain on derivative financial instruments	115	209	209
Unrecognized pension and postretirement cost	7,200	(20,258)	12,875
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI, Pension and Other Postretirement Benefit Plans, for Net Gain (Loss), before Tax		(1,452)
Amortization of net unrecognized pension and postretirement income (3)	2,869	627	2,019
Total Other Comprehensive Loss	(6,608)	30,186	(66,178)
Tax Effect
Unrealized loss on securities	4,155	(18,167)	26,712
Reclassification adjustment for securities gains included in net income (1)	3,174	714	2,801
Non-credit related unrealized gains on other-than-temporarily impaired debt securities	(129)	(420)	(1,065)
Unrealized gain on derivative financial instruments	(40)	(73)	(73)
Unrecognized pension and postretirement cost	(2,520)	7,090	(4,506)
Reclass adjustment for postretirement plan gain included in net income, tax		508
Amortization of net unrecognized pension and postretirement income (3)	(1,005)	(219)	(707)
Total Other Comprehensive Loss	2,313	(10,567)	23,162
Net of Tax Amount
Unrealized loss on securities	(7,717)	33,734	(49,607)
Reclassification adjustment for securities gains included in net income (1)	(5,892)	(1,327)	(5,203)
Non-credit related unrealized gains on other-than-temporarily impaired debt securities	239	780	1,977
Unrealized gain on derivative financial instruments	75	136	136
Unrecognized pension and postretirement cost	4,680	(13,168)	8,369
Reclass adjustment for postretirement plan gain included in net income, net of tax	0	(944)	0
Amortization of net unrecognized pension and postretirement income (3)	1,864	408	1,312
Total Other Comprehensive Loss	$ (4,295)	$ 19,619	$ (43,016)