Derivative Financial Instruments (Details) (USD $)	3 Months Ended	12 Months Ended
	Mar. 31, 2013 item	Dec. 31, 2012 item
Derivative Financial Instruments [Abstract]
Interest rate swaps designated as cash flow hedges, notional amount	$ 10,000,000	$ 10,000,000
Fair values of effective portion of hedges reflected in Other Comprehensive Income	(983,000)	(1,060,000)
Number of interest rate derivative positions	2	2
Interest rate derivatives, combined notional amount	$ 28,380,000	$ 28,630,000