Accumulated Other Comprehensive Income (Details 2) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015	Jun. 30, 2016	Dec. 31, 2015	Jun. 30, 2015	Dec. 31, 2014
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Accumulated Other Comprehensive Income (Loss), Net of Tax	$ (2,412)	$ (8,758)	$ (2,412)	$ (8,758)	$ (3,493)	$ (9,401)	$ (14,048)	$ (14,529)
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent	1,081	5,290	6,989	5,771
Net securities gains (losses)	13	9	26	23
Income tax expense	(3,015)	(2,927)	(16,527)	(8,098)
Unrealized gain (loss) on securities, net of tax	8,162	8,398	30,069	23,082
Change in funded status of post retirement benefits	304	819	912	4,102
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	313	826	929	4,117
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	13,783	8,660	13,783	8,660	13,120	6,083	4,429	7,164
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent	663	4,231	7,700	1,496
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	1,347	3,287	1,347	3,287	1,233	2,970	3,047	3,114
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent	114	240	(1,623)	173
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	15,130	11,947	15,130	11,947	14,353	9,053	7,476	10,278
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent	777	4,471	6,077	1,669
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)	13	9	26	23
Income tax expense	4	2	9	8
Unrealized gain (loss) on securities, net of tax	9	7	17	15
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	(17,542)	(20,705)	(17,542)	(20,705)	$ (17,846)	$ (18,454)	$ (21,524)	$ (24,807)
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent	304	819	912	4,102
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	609	2,735
Unrealized gain (loss) on securities, net of tax	304	819	912	4,102
Change in funded status of post retirement benefits	$ 507	$ 1,365	$ 1,521	$ 6,837