Derivative Financial Instruments (Details) (USD $)	9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Dec. 31, 2009
Derivative Financial Instruments
Notional amount of interest rate swap agreement			$ 8,000,000
Fixed rate payable on notional amount (as a percent)	4.06%
After-tax unrealized loss on cash flow hedge in accumulated other comprehensive income	977,000	888,000
Cash flow hedge liability	1,600,000	1,400,000
Collateral required to be provided	$ 1,600,000	$ 1,400,000