Accumulated Other Comprehensive Income (Details 2) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Net securities gains (losses)	$ 3	$ 27	$ 5	$ 44
Income tax expense	(2,656)	(3,385)	(8,941)	(10,592)
Unrealized gain (loss) on securities, net of tax	11,313	8,794	35,527	26,515
Change in funded status of post retirement benefits	281	184	$ 843	$ 551
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	(279)	(166)
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)	3	27
Income tax expense	(1)	(9)
Unrealized gain (loss) on securities, net of tax	2	18
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	81	117
Unrealized gain (loss) on securities, net of tax	(281)	(184)
Change in funded status of post retirement benefits	$ (362)	$ (301)