Accumulated Other Comprehensive Income (Details 2) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Net securities gains (losses)	$ 15	$ 10	$ 17	$ 13
Income tax expense	(3,193)	(2,846)	(7,207)	(13,512)
Unrealized gain (loss) on securities, net of tax	8,352	8,232	17,721	21,907
Change in funded status of post retirement benefits	184	304	367	608
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	(174)	(297)	(356)	(600)
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)	15	10	17	13
Income tax expense	(5)	(3)	(6)	(5)
Unrealized gain (loss) on securities, net of tax	10	7	11	8
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	117	203	235	406
Unrealized gain (loss) on securities, net of tax	(184)	(304)	(367)	(608)
Change in funded status of post retirement benefits	$ (301)	$ (507)	$ (602)	$ (1,014)