CONSOLIDATED BALANCE SHEETS (Parenthetical) (USD $)	Mar. 31, 2013	Dec. 31, 2012
CONSOLIDATED BALANCE SHEETS
Common stock, par value (in dollars per share)	$ 0.001	$ 0.001
Common stock, shares authorized (in shares)	200,000,000	200,000,000
Common stock, shares issued (in shares)	91,545,084	91,333,092
Common stock, shares outstanding (in shares)	91,545,084	91,333,092