Accumulated Other Comprehensive Income (Loss) - Changes in Balances of Each Component (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Accumulated Other Comprehensive Income [Roll Forward]
AOCI - beginning balance			$ (1,630)	$ (6,410)
Other comprehensive income before reclassifications			(1,351)	11,394
Amounts reclassified from accumulated other comprehensive income			(633)	(834)
Period change	$ 2,876	$ (60)	(1,984)	10,560
AOCI - ending balance	(3,614)	4,150	(3,614)	4,150
Unrealized Gains (Losses) on Securities Available for Sale
Accumulated Other Comprehensive Income [Roll Forward]
AOCI - beginning balance			14,098	1,566
Other comprehensive income before reclassifications			117	11,338
Amounts reclassified from accumulated other comprehensive income			(1,331)	(1,518)
Period change			(1,214)	9,820
AOCI - ending balance	12,884	11,386	$ 12,884	11,386
Unrealized Gains (Losses) on Securities Available for Sale for which a Portion of Other-Than-Temporary Impairment has been Recognized in Income
Accumulated Other Comprehensive Income [Roll Forward]
AOCI - beginning balance				(1,847)
Other comprehensive income before reclassifications				$ 1,701
Amounts reclassified from accumulated other comprehensive income
Period change			$ 0	$ 1,701
AOCI - ending balance	0	(146)	0	(146)
Unrealized Gains (Losses) on Cash Flow Hedges
Accumulated Other Comprehensive Income [Roll Forward]
AOCI - beginning balance			(2,182)	(501)
Other comprehensive income before reclassifications			(1,468)	(1,645)
Amounts reclassified from accumulated other comprehensive income			698	684
Period change			(770)	(961)
AOCI - ending balance	(2,952)	(1,462)	(2,952)	(1,462)
Unrealized Gains (Losses) on Defined Benefit Plans
Accumulated Other Comprehensive Income [Roll Forward]
AOCI - beginning balance			$ (13,546)	$ (5,628)
Other comprehensive income before reclassifications
Amounts reclassified from accumulated other comprehensive income
Period change			$ 0	$ 0
AOCI - ending balance	$ (13,546)	$ (5,628)	$ (13,546)	$ (5,628)