Regulatory Capital (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012	Mar. 31, 2012	Dec. 31, 2011
Regulatory Capital [Abstract]
Allowance for loan losses to risk-weighted assets (in hundredths)	1.25%
Minimum ratio of Tier 1 capital to risk-weighted assets (in hundredths)	4.00%
Minimum ratio of total capital (Tier 1 capital plus Tier 2 capital) to risk-weighted assets (in hundredths)	8.00%
Minimum Ratio of Tier 1 Leverage Capital to adjusted quarterly average total assets	3.00%
Minimum Tier 1 risk-based capital ratio required to be considered well capitalized (in hundredths)	6.00%
Minimum total capital ratio required to be considered well capitalized (in hundredths)	10.00%
Minimum Tier 1 leverage capital ratio required to be considered well capitalized (in hundredths)	5.00%
Regulatory Capital [Abstract]
Shareholders' equity	$ 94,204	$ 82,006	$ 78,513	$ 77,960
Goodwill and other intangibles	(16,924)	(6,019)
Accumulated other comprehensive income	(4,000)	(4,721)
Tier 1 risk-based capital	73,280	71,266
Eligible allowance for loan losses	3,404	3,437
Total risk-based capital	$ 76,684	$ 74,703
Capital Ratios [Abstract]
Total risk-based (8% required) (in hundredths)	13.40%	15.86%
Tier 1 risk-based (4% required) (in hundredths)	12.80%	15.13%
Leverage (3% required) (in hundredths)	8.13%	8.98%