Other Comprehensive Income, Reclassifications out of accumulated other comprehensive income (loss) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Reclassification Adjustment Out of Accumulated Other Comprehensive Income [Line Items]
Net gain on securities transactions	$ 376	$ 0	$ 382	$ 1,434
Salaries and employee benefits	8,272	7,935	23,876	23,760
Income taxes	6,532	6,077	20,875	17,373
Net income	10,714	10,252	33,533	29,183
Reclassification Out of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment Out of Accumulated Other Comprehensive Income [Line Items]
Net income	127	(30)	274	768
Unrealized Gain (Losses) on Securities Available For Sale [Member] | Reclassification Out of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment Out of Accumulated Other Comprehensive Income [Line Items]
Net gain on securities transactions	376	0	382	1,434
Income taxes	(151)	0	(153)	(574)
Net income	225	0	229	860
Amortization of Pension and Postretirement Benefit Items [Member] | Reclassification Out of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment Out of Accumulated Other Comprehensive Income [Line Items]
Income taxes	64	21	(29)	61
Net income	(98)	(30)	45	(92)
Amortization of Net Actuarial Gain (Loss) [Member] | Reclassification Out of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment Out of Accumulated Other Comprehensive Income [Line Items]
Salaries and employee benefits	77	(117)	223	(350)
Amortization Of Prior Service Credit [Member] | Reclassification Out of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment Out of Accumulated Other Comprehensive Income [Line Items]
Salaries and employee benefits	$ (239)	$ 66	$ (149)	$ 197