Accumulated Other Comprehensive (Loss) Income, Reclassifications out of accumulated other comprehensive income (loss) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Reclassification Adjustment Out of Accumulated Other Comprehensive Income [Line Items]
Net gain on securities transactions	$ 668	$ 0	$ 668	$ 249
Salaries and employee benefits	8,934	8,164	17,937	16,645
Income taxes	6,260	6,467	12,366	12,883
Net income	10,464	10,727	20,875	21,442
Reclassification Out of Accumulated Other Comprehensive Income (Loss) [Member]
Reclassification Adjustment Out of Accumulated Other Comprehensive Income [Line Items]
Net income	417	(49)	384	116
Net Unrealized Holding Gain (Loss) on Securities Available for Sale [Member] | Reclassification Out of Accumulated Other Comprehensive Income (Loss) [Member]
Reclassification Adjustment Out of Accumulated Other Comprehensive Income [Line Items]
Net gain on securities transactions	668	0	668	249
Income taxes	(267)	0	(267)	(100)
Net income	401	0	401	149
Net Change in Net Actuarial Loss and Prior Service Credit on Pension and Postretirement Benefit Plans, Net of Tax [Member] | Reclassification Out of Accumulated Other Comprehensive Income (Loss) [Member]
Reclassification Adjustment Out of Accumulated Other Comprehensive Income [Line Items]
Income taxes	(12)	33	11	22
Net income	16	(49)	(17)	(33)
Amortization of Net Actuarial Loss [Member] | Reclassification Out of Accumulated Other Comprehensive Income (Loss) [Member]
Reclassification Adjustment Out of Accumulated Other Comprehensive Income [Line Items]
Salaries and employee benefits	50	(15)	17	(10)
Amortization of Prior Service Cost [Member] | Reclassification Out of Accumulated Other Comprehensive Income (Loss) [Member]
Reclassification Adjustment Out of Accumulated Other Comprehensive Income [Line Items]
Salaries and employee benefits	$ (22)	$ (67)	$ (45)	$ (45)