Stockholders' Equity (Components of Accumulated Other Comprehensive Income (Loss)) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance			$ (80,595)	$ (50,074)
Net change in unrealized gain	$ (5,604)	$ 15,131	39,997	2,174
Reclassification of net (gain) losses realized and included in earnings	1,158	802	2,960	2,208
Valuation adjustment for employee benefit plans	(6,347)	4,963	(6,347)	(959)
Amortization of unrealized net loss on securities transferred to HTM	1,108	1,023	2,736	2,609
Income tax (benefit) expense	(3,537)	8,002	14,440	2,125
Ending Balance	(55,689)	(46,167)	(55,689)	(46,167)
Available for Sale Securities [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance			4,268	18,001
Net change in unrealized gain			38,835	163
Reclassification of net (gain) losses realized and included in earnings			(1,435)	(165)
Valuation adjustment for employee benefit plans
Amortization of unrealized net loss on securities transferred to HTM
Income tax (benefit) expense			13,701	(73)
Ending Balance	27,967	18,072	27,967	18,072
HTM Securities Transferred from AFS [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance			(16,795)	(19,074)
Net change in unrealized gain
Reclassification of net (gain) losses realized and included in earnings
Valuation adjustment for employee benefit plans
Amortization of unrealized net loss on securities transferred to HTM			2,736	2,609
Income tax (benefit) expense			1,029	953
Ending Balance	(15,088)	(17,418)	(15,088)	(17,418)
Employee Benefit Plans [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance			(67,890)	(48,626)
Net change in unrealized gain
Reclassification of net (gain) losses realized and included in earnings			4,395	2,373
Valuation adjustment for employee benefit plans			(6,347)	(959)
Amortization of unrealized net loss on securities transferred to HTM
Income tax (benefit) expense			(714)	513
Ending Balance	(69,128)	(47,725)	(69,128)	(47,725)
Loss on Effective Cash Flow Hedges [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance			(178)	(375)
Net change in unrealized gain			1,162	2,011
Reclassification of net (gain) losses realized and included in earnings
Valuation adjustment for employee benefit plans
Amortization of unrealized net loss on securities transferred to HTM
Income tax (benefit) expense			424	732
Ending Balance	$ 560	$ 904	$ 560	$ 904