CONDENSED BALANCE SHEETS (Parenthetical) (USD $) In Thousands, except Per Share data, unless otherwise specified	Mar. 31, 2012	Dec. 31, 2011
Preferred stock, par value (in dollars per share)	$ 0.0001	$ 0.0001
Preferred stock, shares authorized	5,000	5,000
Preferred stock, shares issued	0	0
Common stock, par value (in dollars per share)	$ 0.0001	$ 0.0001
Common stock, shares authorized	100,000	53,093
Common stock, shares issued	19,791	1,559
Common stock, shares outstanding	19,791	1,559
Series A redeemable convertible preferred stock
Redeemable convertible preferred stock, par value (in dollars per share)	$ 0.0001	$ 0.0001
Redeemable convertible preferred stock, shares authorized	0	16,000
Redeemable convertible preferred stock, shares issued	0	16,000
Redeemable convertible preferred stock, shares outstanding	0	16,000
Series B redeemable convertible preferred stock
Redeemable convertible preferred stock, par value (in dollars per share)	$ 0.0001	$ 0.0001
Redeemable convertible preferred stock, shares authorized		16,025
Redeemable convertible preferred stock, shares issued		16,025
Redeemable convertible preferred stock, shares outstanding		16,025
Series C redeemable convertible preferred stock
Redeemable convertible preferred stock, par value (in dollars per share)	$ 0.0001	$ 0.0001
Redeemable convertible preferred stock, shares authorized		9,068
Redeemable convertible preferred stock, shares issued		9,068
Redeemable convertible preferred stock, shares outstanding		9,068