Accumulated Other Comprehensive Income (Details 2) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Reclassification Adjustment out of Accumulated Other Comprehensive Income on Derivatives [Line Items]
Net securities gains (losses)	$ 2	$ 3
Income tax expense	(4,014)	(10,666)
Unrealized gain (loss) on securities, net of tax	9,369	13,675
Change in funded status of post retirement benefits	183	304
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	184	305
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	3
Income tax expense	(1)	(2)
Unrealized gain (loss) on securities, net of tax	1	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	(118)	(203)
Unrealized gain (loss) on securities, net of tax	183	304
Change in funded status of post retirement benefits	$ 301	$ 507