Consolidated Balance Sheets (Parenthetical) (USD $)	Mar. 31, 2013	Dec. 31, 2012
Common Stock
Common Stock, Par Value	$ 0.01	$ 0.01
Common Stock, Shares Authorized	640,000,000	640,000,000
Common Stock, Shares Issued	272,366,287	271,958,495
Treasury Stock
Common Stock Held in Treasury, Shares	308,010	326,264