Accumulated Other Comprehensive Income (Details 2) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Net securities gains (losses)	$ 0	$ 2
Income tax expense	(1,939)	(4,014)
Unrealized gain (loss) on securities, net of tax	8,953	9,369
Change in funded status of post retirement benefits	281	183
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	(281)	(182)
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)	0	2
Income tax expense	0	(1)
Unrealized gain (loss) on securities, net of tax	0	1
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	118
Unrealized gain (loss) on securities, net of tax	(281)	(183)
Change in funded status of post retirement benefits	$ (362)	$ (301)