Accumulated Other Comprehensive Income (Details 2) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015	Mar. 31, 2016	Dec. 31, 2015	Mar. 31, 2015	Dec. 31, 2014
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Accumulated Other Comprehensive Income (Loss), Net of Tax	$ (3,493)	$ (14,048)	$ (3,493)	$ (14,048)	$ (5,059)	$ (9,401)	$ (7,303)	$ (14,529)
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent	1,566	(6,745)	5,908	481
Net securities gains (losses)	10	10	13	14
Income tax expense	(2,846)	(2,319)	(13,512)	(5,171)
Unrealized gain (loss) on securities, net of tax	8,232	6,923	21,907	14,684
Change in funded status of post retirement benefits	304	819	608	3,283
Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Unrealized gain (loss) on securities, net of tax	311	826	616	3,291
Unrealized gains losses on securities available-for-sale without other than temporary impairment [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Accumulated Other Comprehensive Income (Loss), Net of Tax	13,120	4,429	13,120	4,429	10,880	6,083	11,448	7,164
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent	2,240	(7,019)	7,037	(2,735)
Unrealized gains losses on securities available-for-sale with other than temporary impairment [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Accumulated Other Comprehensive Income (Loss), Net of Tax	1,233	3,047	1,233	3,047	2,211	2,970	3,592	3,114
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent	(978)	(545)	(1,737)	(67)
Accumulated Net Unrealized Investment Gain (Loss) [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Accumulated Other Comprehensive Income (Loss), Net of Tax	14,353	7,476	14,353	7,476	13,091	9,053	15,040	10,278
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent	1,262	(7,564)	5,300	(2,802)
Accumulated Net Unrealized Investment Gain (Loss) [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Net securities gains (losses)	10	10	13	14
Income tax expense	3	3	5	6
Unrealized gain (loss) on securities, net of tax	7	7	8	8
Accumulated Defined Benefit Plans Adjustment [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Accumulated Other Comprehensive Income (Loss), Net of Tax	(17,846)	(21,524)	(17,846)	(21,524)	$ (18,150)	$ (18,454)	$ (22,343)	$ (24,807)
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent	304	819	608	3,283
Accumulated Defined Benefit Plans Adjustment [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Income tax expense	203	546	406	2,189
Unrealized gain (loss) on securities, net of tax	304	819	608	3,283
Change in funded status of post retirement benefits	$ 507	$ 1,365	$ 1,014	$ 5,472