Derivative Instruments (Narrative) (Details) (USD $)	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009	Apr. 30, 2011
Derivative Instruments
Interest rate swap notional amount				$ 50,000,000
Percentage of interest rate swap pays to counterparty				5.365%
Unrealized gain on interest rate swap, net of income tax	515,000	1,334,000	1,002,000
Accumulated other comprehensive loss, net of income taxes	$ 0	$ 515,000