Accumulated Other Comprehensive Income (Loss) (Components of AOCI) (Details) - USD ($) $ in Thousands		3 Months Ended
		Mar. 31, 2016	Mar. 31, 2015
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance		$ (64,440)	$ (52,981)
Other comprehensive income before reclassifications		42,454	18,956
Amounts reclassified from accumulated other comprehensive (loss) income		(1,838)	(1,386)
Net current period other comprehensive income		40,616	17,570
Ending balance		(23,824)	(35,411)
Unrealized Loss on Cash Flow Hedges
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	[1]	(892)	(2,664)
Other comprehensive income before reclassifications	[1]	437	354
Amounts reclassified from accumulated other comprehensive (loss) income	[1]	0	0
Net current period other comprehensive income	[1]	437	354
Ending balance	[1]	(455)	(2,310)
Unrealized Gains on Investment Securities Available for Sale
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	[1]	(15,125)	5,098
Other comprehensive income before reclassifications	[1]	42,017	18,602
Amounts reclassified from accumulated other comprehensive (loss) income	[1]	(2,858)	(3,149)
Net current period other comprehensive income	[1]	39,159	15,453
Ending balance	[1]	24,034	20,551
Defined Benefit Pension Items
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	[1]	(48,423)	(55,415)
Other comprehensive income before reclassifications	[1]	0	0
Amounts reclassified from accumulated other comprehensive (loss) income	[1]	1,020	1,763
Net current period other comprehensive income	[1]	1,020	1,763
Ending balance	[1]	$ (47,403)	$ (53,652)

[1] All amounts are net of tax.