Reclassification Adjustments Out of Other Comprehensive (Loss) Income (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Gain (Loss) on Sale of Securities, Net	$ 329	$ 26	$ 1,413	$ 578
Salaries and employee benefits	29,267	26,641	85,474	78,358
Income tax expense	8,632	5,513	19,413	17,049
Net Income	19,257	14,535	43,822	41,442
Total reclassification during the period, net of tax	229	583	506	1,279
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	(329)	(26)	(1,413)	(578)
Income tax expense	132	10	565	231
Net Income	(197)	(16)	(848)	(347)
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	283	390	890	1,076
Net Income	426	599	1,354	1,626
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	1,044	2,411	2,869
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	$ (56)	$ (55)	$ (167)	$ (167)