Financial Instruments with Off-Balance Sheet Risk and Derivative Transactions (Details) (USD $)	6 Months Ended	12 Months Ended
	Jun. 30, 2012	Dec. 31, 2011
Not designated as hedging instruments
Financial Instruments with Off-Balance Sheet Risk and Derivative Transactions
Asset Derivatives, Fair Value	$ 3,447,000	$ 3,179,000
Liability Derivatives, Fair Value	2,622,000	3,202,000
Interest rate swap
Financial Instruments with Off-Balance Sheet Risk and Derivative Transactions
Financial instruments with off-balance sheet risk and derivative transactions	5,100,000	5,200,000
Investment securities pledged with financial institutions, number	2
Interest rate swap | Not designated as hedging instruments
Financial Instruments with Off-Balance Sheet Risk and Derivative Transactions
Weighted average maturity (in years)	1 year 8 months 26 days	2 years 2 months 26 days
Notional or Contractual Amount	115,728,000	117,756,000
Asset Derivatives, Fair Value	2,537,000	3,072,000
Liability Derivatives, Fair Value	2,606,000	3,152,000
Commitments | Not designated as hedging instruments
Financial Instruments with Off-Balance Sheet Risk and Derivative Transactions
Notional or Contractual Amount	259,944,000	237,970,000
Asset Derivatives, Fair Value	910,000	107,000
Forward contracts | Not designated as hedging instruments
Financial Instruments with Off-Balance Sheet Risk and Derivative Transactions
Notional or Contractual Amount	40,500,000	26,000,000
Liability Derivatives, Fair Value	$ 16,000	$ 50,000