Accumulated Other Comprehensive Income (Loss) (Components of AOCI) (Details) - USD ($) $ in Thousands		3 Months Ended
		Mar. 31, 2017	Mar. 31, 2016
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance		$ (135,192)	$ (64,440)
Other comprehensive loss before reclassifications		22,677	42,454
Amounts reclassified from accumulated other comprehensive income (loss)		1,574	(1,838)
Net current period other comprehensive (loss) income		24,251	40,616
Ending balance		(110,941)	(23,824)
Unrealized Loss on Cash Flow Hedges
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	[1]	0	(892)
Other comprehensive loss before reclassifications	[1]	0	437
Amounts reclassified from accumulated other comprehensive income (loss)	[1]	0	0
Net current period other comprehensive (loss) income	[1]	0	437
Ending balance	[1]	0	(455)
Unrealized Gains on Investment Securities Available for Sale
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	[1]	(45,875)	(15,125)
Other comprehensive loss before reclassifications	[1]	22,677	42,017
Amounts reclassified from accumulated other comprehensive income (loss)	[1]	15	(2,858)
Net current period other comprehensive (loss) income	[1]	22,692	39,159
Ending balance	[1]	(23,183)	24,034
Defined Benefit Pension Items
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	[1]	(89,317)	(48,423)
Other comprehensive loss before reclassifications	[1]	0	0
Amounts reclassified from accumulated other comprehensive income (loss)	[1]	1,559	1,020
Net current period other comprehensive (loss) income	[1]	1,559	1,020
Ending balance	[1]	$ (87,758)	$ (47,403)

[1] All amounts are net of tax.