Fair Value Measurement (Details) (USD $) In Thousands, unless otherwise specified	9 Months Ended
	Sep. 30, 2013	Dec. 31, 2012
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Discount for selling costs (in hundredths)	10.00%
Available-for-sale securities [Abstract]
Available-for-sale securities	$ 358,675	$ 424,617	[1]
Minimum [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Period when new appraisals are received (in weeks)	4
Maximum [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Period when new appraisals are received (in weeks)	6
Fair Value, Measurements, Recurring [Member]
Available-for-sale securities [Abstract]
U.S. Government sponsored enterprises	11,419	13,424
Obligations of state and political subdivisions	66,524	87,421
GSE mortgage-backed securities	152,574	178,819
Other asset-backed securities	25,722
Collateralized mortgage obligations: residential	74,315	101,986
Collateralized mortgage obligations: commercial	27,530	29,761
Other asset-backed securities		12,742
Collateralized debt obligation	591	464
Available-for-sale securities	358,675	424,617
Fair Value, Measurements, Recurring [Member] | Level 1 [Member]
Available-for-sale securities [Abstract]
U.S. Government sponsored enterprises	0	0
Obligations of state and political subdivisions	0	0
GSE mortgage-backed securities	0	0
Other asset-backed securities	0
Collateralized mortgage obligations: residential	0	0
Collateralized mortgage obligations: commercial	0	0
Other asset-backed securities		0
Collateralized debt obligation	0	0
Available-for-sale securities	0	0
Fair Value, Measurements, Recurring [Member] | Level 2 [Member]
Available-for-sale securities [Abstract]
U.S. Government sponsored enterprises	11,419	13,424
Obligations of state and political subdivisions	66,524	87,421
GSE mortgage-backed securities	152,574	178,819
Other asset-backed securities	25,722
Collateralized mortgage obligations: residential	74,315	101,986
Collateralized mortgage obligations: commercial	27,530	29,761
Other asset-backed securities		12,742
Collateralized debt obligation	591	464
Available-for-sale securities	358,675	424,617
Fair Value, Measurements, Recurring [Member] | Level 3 [Member]
Available-for-sale securities [Abstract]
U.S. Government sponsored enterprises	0	0
Obligations of state and political subdivisions	0	0
GSE mortgage-backed securities	0	0
Other asset-backed securities	0
Collateralized mortgage obligations: residential	0	0
Collateralized mortgage obligations: commercial	0	0
Other asset-backed securities		0
Collateralized debt obligation	0	0
Available-for-sale securities	0	0
Fair Value, Measurements, Nonrecurring [Member]
Assets and Liabilities Measured on Nonrecurring Basis
Acquired loans with deteriorated credit quality	1,016	4,521
Other real estate	6,672	7,496
Impaired loans, excluding acquired loans	2,152	2,245
Total	9,840	14,262
Fair Value, Measurements, Nonrecurring [Member] | Level 1 [Member]
Assets and Liabilities Measured on Nonrecurring Basis
Acquired loans with deteriorated credit quality	0	0
Other real estate	0	0
Impaired loans, excluding acquired loans	0
Total	0	0
Fair Value, Measurements, Nonrecurring [Member] | Level 2 [Member]
Assets and Liabilities Measured on Nonrecurring Basis
Acquired loans with deteriorated credit quality	0	0
Other real estate	6,672	7,496
Impaired loans, excluding acquired loans	2,152	2,245
Total	8,824	9,741
Fair Value, Measurements, Nonrecurring [Member] | Level 3 [Member]
Assets and Liabilities Measured on Nonrecurring Basis
Acquired loans with deteriorated credit quality	1,016	4,521
Other real estate	0	0
Impaired loans, excluding acquired loans	0	0
Total	$ 1,016	$ 4,521

[1] Derived from audited financial statements.