Accumulated Other Comprehensive Income (Details 2) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Net securities gains (losses)	$ 2	$ 15	$ 2	$ 17
Income tax expense	(4,346)	(3,193)	(6,285)	(7,207)
Unrealized gain (loss) on securities, net of tax	15,261	8,352	24,214	17,721
Change in funded status of post retirement benefits	281	184	$ (2,302)	$ 367
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)	(174)
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)	2	15
Income tax expense	0	(5)
Unrealized gain (loss) on securities, net of tax	2	10
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)