CONDENSED CONSOLIDATED BALANCE SHEETS (unaudited) (Parenthetical) (USD $) In Thousands, except Per Share data, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012
Stockholders' equity:
Preferred stock, par value (in dollars per share)	$ 0.001	$ 0.001
Preferred stock, shares authorized (in shares)	15,000	15,000
Preferred stock, shares issued (in shares)	0	0
Preferred stock, shares outstanding (in shares)	0	0
Common stock, par value (in dollars per share)	$ 0.001	$ 0.001
Common stock, shares authorized (in shares)	32,500	32,500
Common stock, shares issued (in shares)	20,548	19,696
Common stock, shares outstanding (in shares)	20,548	19,696