Derivative Financial Instruments (Details) (USD $)	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012	Dec. 31, 2012	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%
Variable rate basis, variable rate receivable on notional amount	three-month LIBOR
After-tax unrealized gain on cash flow hedge in other comprehensive income	63,000	69,000
Cash flow hedge liability	1,400,000	1,300,000
Ineffectiveness in the cash flow hedge	0	0
Collateral required to be provided	1,600,000	1,400,000	354,000
Aggregate notional amount of non-designated interest rate swaps	4,500,000
Fair value of non-designated interest rate swaps recorded in other assets and other liabilities	290,000
Termination value of obligations under agreements	$ 297,000
Savannah
Derivative Financial Instruments
Number of interest rate swaps contracts that were classified as non-designated hedges acquired through merger	2