Annual report pursuant to Section 13 and 15(d)

CONSOLIDATED BALANCE SHEETS (Parenthetical)

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CONSOLIDATED BALANCE SHEETS (Parenthetical) (USD $)
Dec. 31, 2012
Dec. 31, 2011
Dec. 31, 2010
Common stock, par value $ 0.001 $ 0.001  
Common stock, shares authorized 300,000,000 300,000,000  
Common stock, shares issued 118,502,752 117,593,329  
Common stock, shares outstanding 114,949,667 114,201,737  
Treasury stock, shares 3,553,085 3,391,592 3,359,859