Accumulated Other Comprehensive Income (Loss) (Components of AOCI) (Details) - USD ($) $ in Thousands		3 Months Ended		6 Months Ended
		Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance		$ (110,941)	$ (23,824)	$ (135,192)	$ (64,440)
Other comprehensive income before reclassifications		8,646	15,370	31,323	57,824
Amounts reclassified from accumulated other comprehensive (loss) income		(548)	(6,573)	1,026	(8,411)
Net current period other comprehensive income		8,098	8,797	32,349	49,413
Ending balance		(102,843)	(15,027)	(102,843)	(15,027)
Unrealized Loss on Cash Flow Hedges
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	[1]	0	(455)	0	(892)
Other comprehensive income before reclassifications	[1]	0	455	0	892
Amounts reclassified from accumulated other comprehensive (loss) income	[1]	0	0	0	0
Net current period other comprehensive income	[1]	0	455	0	892
Ending balance	[1]	0	0	0	0
Unrealized Gains on Investment Securities Available for Sale
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	[1]	(23,183)	24,034	(45,875)	(15,125)
Other comprehensive income before reclassifications	[1]	8,646	14,915	31,323	56,932
Amounts reclassified from accumulated other comprehensive (loss) income	[1]	(2,111)	(7,736)	(2,096)	(10,594)
Net current period other comprehensive income	[1]	6,535	7,179	29,227	46,338
Ending balance	[1]	(16,648)	31,213	(16,648)	31,213
Defined Benefit Pension Items
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning balance	[1]	(87,758)	(47,403)	(89,317)	(48,423)
Other comprehensive income before reclassifications	[1]	0	0	0	0
Amounts reclassified from accumulated other comprehensive (loss) income	[1]	1,563	1,163	3,122	2,183
Net current period other comprehensive income	[1]	1,563	1,163	3,122	2,183
Ending balance	[1]	$ (86,195)	$ (46,240)	$ (86,195)	$ (46,240)

[1] All amounts are net of tax.