Condensed Consolidated Balance Sheets (Parenthetical) (USD $)	Jun. 30, 2013	Dec. 31, 2012
Common stock, par value	$ 0.001	$ 0.001
Common stock, shares authorized	300,000,000	300,000,000
Common stock, shares issued	118,997,209	118,502,752
Common stock, shares outstanding	115,313,546	114,949,667
Treasury stock, shares	3,683,663	3,553,085