Commitments and Off-Balance Sheet Risk (Details) (USD $)	Sep. 30, 2012	Dec. 31, 2011
Summary of contractual amounts of financial instruments with off-balance sheet risk
Contractual amounts of financial instruments with off-balance sheet risk	$ 333,477,000	$ 254,130,000
Commercial unused lines of credit [Member]
Summary of contractual amounts of financial instruments with off-balance sheet risk
Contractual amounts of financial instruments with off-balance sheet risk	195,363,000	171,683,000
Unused lines of credit secured by 1 - 4 family residential properties [Member]
Summary of contractual amounts of financial instruments with off-balance sheet risk
Contractual amounts of financial instruments with off-balance sheet risk	24,063,000	24,663,000
Credit card unused lines of credit [Member]
Summary of contractual amounts of financial instruments with off-balance sheet risk
Contractual amounts of financial instruments with off-balance sheet risk	8,149,000	7,565,000
Other consumer unused lines of credit [Member]
Summary of contractual amounts of financial instruments with off-balance sheet risk
Contractual amounts of financial instruments with off-balance sheet risk	4,489,000	3,367,000
Commitments to extend credit [Member]
Summary of contractual amounts of financial instruments with off-balance sheet risk
Contractual amounts of financial instruments with off-balance sheet risk	90,448,000	30,929,000
Standby letters of credit [Member]
Summary of contractual amounts of financial instruments with off-balance sheet risk
Contractual amounts of financial instruments with off-balance sheet risk	$ 10,965,000	$ 15,923,000