Income Taxes (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Principal components of income tax expense [Abstract]
Current taxes	$ 8,494	$ 7,076	$ 5,202
Deferred taxes	(848)	(1,341)	(2,253)
Income tax expense (benefit)	7,646	5,735	2,949
Reconciliation of Income Tax Computed at Federal Statutory Rates to Income Tax Provision [Abstract]
Income tax computed at federal statutory rates	8,410	6,362	3,760
Tax effect of exclusion of interest income on obligations of states and political subdivisions	(1,631)	(1,652)	(1,516)
Reduction of interest expense incurred to carry tax-exempt assets	78	98	100
State income taxes, net of federal tax benefit	1,133	1,114	787
Tax effect of dividends-received deduction on preferred stock	0	0	(5)
Compensation in excess of deductible limits	0	41	0
Tax credits	(225)	(180)	(135)
Other	(119)	(48)	(42)
Income tax expense (benefit)	7,646	5,735	2,949
Reconciliation of Federal Statutory Tax Rate to Effective Tax Rate [Abstract]
Income tax computed at federal statutory rates, percent of pre-tax income (in hundredths)	35.00%	34.00%	34.00%
Tax effect of exclusion of interest income on obligations of states and political subdivisions, percent of pre-tax income (in hundredths)	(6.80%)	(8.80%)	(13.70%)
Reduction of interest expense incurred to carry tax-exempt assets, percent of pre-tax income (in hundredths)	0.30%	0.50%	0.90%
State income taxes, net of federal tax benefit, percent of pre-tax income (in hundredths)	4.70%	6.00%	7.10%
Tax effect of dividends-received deduction on preferred stock, percent of pre-tax income (in hundredths)	0.00%	0.00%	(0.10%)
Compensation in excess of deductible limits, percent of pre-tax income (in hundredths)	0.00%	0.20%	0.00%
Tax credits, percent of pre-tax income (in hundredths)	(0.90%)	(1.00%)	(1.20%)
Other, percent of pre-tax income (in hundredths)	(0.50%)	(0.30%)	(0.30%)
Effective income tax rate (in hundredths)	31.80%	30.60%	26.70%
Deferred tax asset [Abstract]
Allowance for loan losses and OREO losses	15,036	14,128
Reserve for indemnification losses	795	647
OREO expenses	226	381
Deferred compensation	2,049	1,916
Other-than-temporary impairment of Fannie Mae and Freddie Mac preferred stock	614	614
Share-based compensation	340	331
Interest on nonaccrual loans	244	119
Cash flow hedges	200	201
Other	1,284	1,240
Deferred tax asset	20,944	19,742
Deferred tax liability [Abstract]
Goodwill and other intangible assets	(2,794)	(2,509)
Depreciation	(59)	(3)
Net unrealized gain on securities available for sale	(3,205)	(2,475)
Deferred tax liability	(6,058)	(4,987)
Net deferred tax asset	$ 14,886	$ 14,755