Balance Sheets (Parenthetical) (USD $) In Thousands, except Share data, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Balance Sheets
Preferred stock, par value (in dollars per share)	$ 0.001	$ 0.001
Preferred stock, authorized shares	10,000,000	10,000,000
Preferred stock, issued shares	8,804	0
Preferred stock, outstanding shares	8,804	0
Preferred stock, liquidation value (in dollars)	$ 17,608
Common stock, par value (in dollars per share)	$ 0.001	$ 0.001
Common stock, authorized shares	90,000,000	90,000,000
Common stock, issued shares	20,023,949	14,748,582
Common stock, outstanding shares	20,023,949	14,748,582