Consolidated Balance Sheets (Unaudited) (Parenthetical) (USD $)	Sep. 30, 2012	Dec. 31, 2011
Common stock, par value	$ 0.01	$ 0.01
Common stock, shares authorized	500,000,000	500,000,000
Common stock, shares issued	143,947,118	143,944,009
Common stock, shares outstanding	139,030,318	139,027,209
Treasury stock, shares	4,916,800	4,916,800