Accumulated Other Comprehensive Income Changes in Other Comprehensive Income (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Equity [Abstract]
Unrealized gain on securities, before tax amount	$ 19,753	$ (18,474)	$ 45,946	$ (3,103)
Unrealized gain on securities, tax effect	(6,914)	6,466	(16,081)	1,087
Unrealized gain on securities, net of tax amount	12,839	(12,008)	29,865	(2,016)
Reclassification adjustment for securities gains included in net income, before tax amount	(76)	(2,413)	(1,023)	(6,558)
Reclassification adjustment for securities gains included in net income, tax effect	27	844	358	2,294
Reclassification adjustment for securities gains included in net income, net of tax amount	(49)	(1,569)	(665)	(4,264)
Non-credit related unrealized gains on other-than-temporarily impaired debt securities, before tax amount				192
Non-credit related unrealized gains on other-than-temporarily impaired debt securities, tax effect				(67)
Non-credit related unrealized gains on other-than-temporarily impaired debt securities, net of tax amount	0	0	0	125
Amortization of unrealized loss on derivative financial instruments, before tax amount	6	52	12	104
Amortization of unrealized loss on derivative financial instruments, tax effect	(2)	(18)	(4)	(36)
Amortization of unrealized loss on derivative financial instruments, net of tax amount	4	34	8	68
Amortization of net unrecognized pension and postretirement items, before tax amount	49	717	766	1,434
Amortization of net unrecognized pension and postretirement items, tax effect	(17)	(251)	(268)	(502)
Amortization of net unrecognized pension and postretirement items, net of tax amount	32	466	498	932
Total Other Comprehensive Income, Before Tax Amount	19,732	(20,118)	45,701	(7,931)
Total Other Comprehensive Income, Tax Effect	(6,906)	7,041	(15,995)	2,776
Other Comprehensive Income (Loss)	$ 12,826	$ (13,077)	$ 29,706	$ (5,155)