Condensed Balance Sheets (Unaudited) (Parenthetical) (USD $) In Thousands, except Share data, unless otherwise specified	Sep. 30, 2014	Dec. 31, 2013
Statement Of Financial Position [Abstract]
Convertible preferred stock, par value	$ 0.0001	$ 0.0001
Convertible preferred stock, shares authorized	5,000,000	135,816,462
Convertible preferred stock, shares issued	0	120,648,174
Convertible preferred stock, shares outstanding	0	120,648,174
Convertible preferred stock, liquidation preference	$ 0	$ 60,392
Common stock, par value	$ 0.0001	$ 0.0001
Common stock, shares authorized	50,000,000	15,652,174
Common stock, shares issued	24,194,808	1,257,311
Common stock, shares outstanding	24,194,808	1,257,311