Consolidated Statements of Comprehensive Income (Unaudited) - AOCI - 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) [Roll Forward]
Other comprehensive income	$ 6,238	$ (8,427)	$ 19,586	$ (5,377)
Accumulated Unrealized Gain (Loss) on Securities Available- for-Sale
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance			(10,271)	(2,950)
Other comprehensive income			16,479	(3,843)
Ending balance	6,208	(6,793)	6,208	(6,793)
Accumulated Unrealized Gain (Loss) on Derivative Instruments
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance			(2,468)	(1,138)
Other comprehensive income			3,107	(1,534)
Ending balance	639	(2,672)	639	(2,672)
Unrecognized Net Pension Costs
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance			(15,650)	(11,767)
Other comprehensive income			0	0
Ending balance	(15,650)	(11,767)	(15,650)	(11,767)
Total Accumulated Other Comprehensive Loss
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance			(28,389)	(15,855)
Other comprehensive income			19,586	(5,377)
Ending balance	$ (8,803)	$ (21,232)	$ (8,803)	$ (21,232)