CONDENSED CONSOLIDATED BALANCE SHEETS (Parenthetical) (USD $)	Sep. 30, 2011	Dec. 31, 2010
Stockholders' Equity
Preferred stock, par value (in dollars per share)	$ 0.01	$ 0.01
Preferred stock, shares authorized (in shares)	50,000,000	50,000,000
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock, shares authorized (in shares)	200,000,000	200,000,000
Common stock, shares issued (in shares)	127,650,083	125,527,846
Common stock, shares outstanding (in shares)	125,221,682	124,316,545
Common stock, unvested restricted shares (in shares)	4,310,364	3,539,751
Treasury stock, shares (in shares)	2,428,401	1,211,301