CONDENSED BALANCE SHEETS (Parenthetical) (USD $) In Thousands, except Per Share data, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012
CONDENSED BALANCE SHEETS
Common stock, par value (in dollars per share)	$ 0.001	$ 0.001
Common stock, shares authorized	90,000	90,000
Common stock, shares outstanding	32,930	32,881