CONSOLIDATED BALANCE SHEETS (Parenthetical) (USD $)	Dec. 31, 2011	Dec. 31, 2010
CONSOLIDATED BALANCE SHEETS (Parenthetical) [Abstract]
Preferred stock, par value (in dollars per share)	$ 0.01	$ 0.01
Preferred stock, shares authorized	50,000,000	50,000,000
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock, shares authorized	200,000,000	200,000,000
Common stock, shares issued (in shares)	127,782,538	125,527,846
Common stock, shares outstanding (in shares)	125,354,137	124,316,545
Treasury stock, shares (in shares)	2,428,401	1,211,301
Common stock, unvested restricted shares (in shares)	4,221,598	3,539,751