Reclassification Adjustments Out of Other Comprehensive (Loss) Income (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Gain (Loss) on Sale of Securities, Net	$ (61)	$ 97	$ 1,084	$ 552
Salaries and employee benefits	29,160	24,992	56,207	51,717
Income tax expense	7,424	5,683	10,781	11,536
Net Income	16,916	13,257	24,565	26,907
Total reclassification during the period, net of tax	463	453	272	696
Accumulated Net Unrealized Investment Gain (Loss) [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Gain (Loss) on Sale of Securities, Net	61	(97)	(1,084)	(552)
Income tax expense	(24)	39	434	221
Net Income	37	(58)	(650)	(331)
Accumulated Defined Benefit Plans Adjustment [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Income tax expense	284	345	614	686
Net Income	426	511	922	1,027
Accumulated Defined Benefit Plans Adjustment [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member] | Amortization of net gains [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Salaries and employee benefits	765	911	1,647	1,824
Accumulated Defined Benefit Plans Adjustment [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member] | Amortization of prior service costs [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Salaries and employee benefits	$ (55)	$ (55)	$ (111)	$ (111)