Common Stock (Details) (USD $)	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010
Class of Stock [Line Items]
Combined common and preferred stock, shares authorized	250,000,000
Common stock, shares authorized	200,000,000	200,000,000
Common stock, par or stated value per share	$ 0.01	$ 0.01
Preferred stock, shares authorized	50,000,000	50,000,000
Preferred stock, par ors stated value per share	$ 0.01	$ 0.01
Common stock reserved for incentive plan awards	2,265,957
Shares paid for tax withholding	2,750	14,453