CONDENSED CONSOLIDATED BALANCE SHEETS (Parenthetical) (USD $)	Mar. 31, 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	118,969,014	118,502,752
Common stock, shares outstanding	115,303,678	114,949,667
Treasury stock, shares	3,665,336	3,553,085