Stockholders' Equity (Components of Accumulated Other Comprehensive Income (Loss)) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance			$ (80,595)	$ (50,074)
Net change in unrealized (loss) gain	$ 16,629	$ (18,370)	45,601	(12,957)
Reclassification of net (gain) losses realized and included in earnings	711	801	1,802	1,406
Valuation adjustment for employee benefit plans		(5,922)		(5,922)
Amortization of unrealized net loss on securities transferred to HTM	830	939	1,628	1,586
Income tax (benefit) expense	6,645	(8,237)	17,977	(5,877)
Ending Balance	(49,541)	(60,084)	(49,541)	(60,084)
Available for Sale Securities [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance			4,268	18,001
Net change in unrealized (loss) gain			41,990	(13,962)
Reclassification of net (gain) losses realized and included in earnings			(1,114)	(165)
Valuation adjustment for employee benefit plans
Amortization of unrealized net loss on securities transferred to HTM
Income tax (benefit) expense			14,970	(5,249)
Ending Balance	30,174	9,123	30,174	9,123
HTM Securities Transferred from AFS [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance			(16,795)	(19,074)
Net change in unrealized (loss) 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			1,628	1,586
Income tax (benefit) expense			625	580
Ending Balance	(15,792)	(18,068)	(15,792)	(18,068)
Employee Benefit Plans [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance			(67,890)	(48,626)
Net change in unrealized (loss) gain
Reclassification of net (gain) losses realized and included in earnings			2,916	1,571
Valuation adjustment for employee benefit plans				(5,922)
Amortization of unrealized net loss on securities transferred to HTM
Income tax (benefit) expense			1,066	(1,574)
Ending Balance	(66,040)	(51,403)	(66,040)	(51,403)
Loss on Effective Cash Flow Hedges [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance			(178)	(375)
Net change in unrealized (loss) gain			3,611	1,005
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			1,316	366
Ending Balance	$ 2,117	$ 264	$ 2,117	$ 264