Accumulated Other Comprehensive Income (Loss) (Components of AOCI) (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		$ (23,824)	$ (35,411)	$ (64,440)	$ (52,981)
Other comprehensive income before reclassifications		15,370	(17,439)	57,824	1,517
Amounts reclassified from accumulated other comprehensive income (loss)		(6,573)	1,691	(8,411)	305
Net current period other comprehensive income		8,797	(15,748)	49,413	1,822
Ending balance		(15,027)	(51,159)	(15,027)	(51,159)
Unrealized Loss on Cash Flow Hedges
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	[1]	(455)	(2,310)	(892)	(2,664)
Other comprehensive income before reclassifications	[1]	455	435	892	789
Amounts reclassified from accumulated other comprehensive income (loss)	[1]	0	0	0	0
Net current period other comprehensive income	[1]	455	435	892	789
Ending balance	[1]	0	(1,875)	0	(1,875)
Unrealized Gains on Investment Securities Available for Sale
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	[1]	24,034	20,551	(15,125)	5,098
Other comprehensive income before reclassifications	[1]	14,915	(17,874)	56,932	728
Amounts reclassified from accumulated other comprehensive income (loss)	[1]	(7,736)	(73)	(10,594)	(3,222)
Net current period other comprehensive income	[1]	7,179	(17,947)	46,338	(2,494)
Ending balance	[1]	31,213	2,604	31,213	2,604
Defined Benefit Pension Items
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	[1]	(47,403)	(53,652)	(48,423)	(55,415)
Other comprehensive income before reclassifications	[1]	0	0	0	0
Amounts reclassified from accumulated other comprehensive income (loss)	[1]	1,163	1,764	2,183	3,527
Net current period other comprehensive income	[1]	1,163	1,764	2,183	3,527
Ending balance	[1]	$ (46,240)	$ (51,888)	$ (46,240)	$ (51,888)

[1] All amounts are net of tax.