Accumulated Other Comprehensive Loss, Net of Tax (Schedule of Other Comprehensive Income (Loss)) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Available-for-sale and transferred securities:
Net unrealized loss during the period	$ (35,701)	$ 34,242	$ (77,524)
Reclassification for net gain included in net income	(609)	(5,499)	(712)
Net non-credit other than temporary impairment	110	1,145	7,277
Amortization of unrealized loss on securities transferred to held-to-maturity	37	60	296
Total available-for-sale and transferred securities	(36,163)	29,948	(70,663)
Derivative instruments:
Net unrealized loss during the period	(4,945)	(19,589)	5,826
Reclassification adjustment for net loss included in net income	8,965	8,100	9,272
Total derivative instruments	4,020	(11,489)	15,098
Defined benefit pension and other postretirement benefit plans:
Current year actuarial loss	(5,367)	(30,683)	26,949
Reclassification adjustment for amortization of net loss included in net income	2,809	37	3,169
Reclassification adjustment for prior service cost included in net income	73	73	73
Total defined benefit pension and postretirement benefit plans	(2,485)	(30,573)	30,191
Available-for-sale and transferred securities:
Net unrealized loss during the period	13,166	(12,469)	27,762
Reclassification for net gain included in net income	223	1,999	255
Net non-credit other than temporary impairment	(40)	(418)	(2,606)
Amortization of unrealized loss on securities transferred to held-to-maturity	(14)	(22)	(106)
Total available-for-sale and transferred securities	13,335	(10,910)	25,305
Derivative instruments:
Net unrealized loss during the period	1,809	7,083	(2,082)
Reclassification adjustment for net loss included in net income	(3,279)	(2,918)	(3,320)
Total derivative instruments	(1,470)	4,165	(5,402)
Defined benefit pension and other postretirement benefit plans:
Current year actuarial loss	1,972	11,187	(9,651)
Reclassification adjustment for amortization of net loss included in net income	(1,027)	(14)	(1,135)
Reclassification adjustment for prior service cost included in net income	(27)	(26)	(26)
Total defined benefit pension and postretirement benefit plans	918	11,147	(10,812)
Available-for-sale and transferred securities:
Net unrealized loss during the period	(22,535)	21,773	(49,762)
Reclassification for net gain included in net income	(386)	(3,500)	(457)
Net non-credit other than temporary impairment	70	727	4,671
Amortization of unrealized loss on securities transferred to held-to-maturity	23	38	190
Total available-for-sale and transferred securities	(22,828)	19,038	(45,358)
Derivative instruments:
Net unrealized gains (losses) on derivative instruments	(3,136)	(12,506)	3,744
Reclassification adjustment for net loss included in net income	5,686	5,182	5,952
Total derivative instruments	2,550	(7,324)	9,696
Defined benefit pension and other postretirement benefit plans:
Current year actuarial loss	(3,395)	(19,496)	17,298
Reclassification adjustment for amortization of net loss included in net income	1,782	23	2,034
Reclassification adjustment for prior service cost included in net income	46	47	47
Total defined benefit pension and postretirement benefit plans	(1,567)	(19,426)	19,379
Other Comprehensive Income (Loss), Pre-Tax Amount	(34,628)	(12,114)	(25,374)
Other Comprehensive Income (Loss), Tax Benefit (Expense)	12,783	4,402	9,091
Other comprehensive loss, net of tax	$ (21,845)	$ (7,712)	$ (16,283)