Consolidated Statements of Comprehensive Income (Unaudited) - AOCI - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Other comprehensive income (loss)	$ 13,348	$ 3,050
Accumulated Unrealized Gain on Securities Available- for-Sale
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning Balance	(10,271)	(2,950)
Other comprehensive income (loss)	10,795	3,481
Ending Balance	524	531
Accumulated Unrealized (Loss) Gain on Derivative Instruments
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning Balance	(2,468)	(1,138)
Other comprehensive income (loss)	2,553	(431)
Ending Balance	85	(1,569)
Unrecognized Net Pension Costs
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning Balance	(15,650)	(11,767)
Other comprehensive income (loss)	0	0
Ending Balance	(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 (loss)	13,348	3,050
Ending Balance	$ (15,041)	$ (12,805)