Condensed Balance Sheets (Parenthetical) (USD $) In Thousands, except Share data, unless otherwise specified	Sep. 30, 2014	Dec. 31, 2013
Redeemable convertible preferred stock, par value	$ 0.00001	$ 0.00001
Redeemable convertible preferred stock, shares authorized	0	5,500,636
Preferred stock, par value	$ 0.00001	$ 0.00001
Preferred stock, shares authorized	25,000,000	0
Preferred stock, shares outstanding	0	0
Common stock, par value	$ 0.00001	$ 0.00001
Common stock, shares authorized	175,000,000	14,700,000
Common stock, shares issued	20,300,243	1,383,345
Common stock, shares outstanding	20,300,243	1,383,345
Treasury Stock, shares	2,553	2,553
Series A redeemable convertible preferred stock
Redeemable convertible preferred stock, shares authorized		734,538
Redeemable convertible preferred stock, shares issued	0	734,538
Redeemable convertible preferred stock, shares outstanding	0	734,538
Redeemable convertible preferred stock, liquidation preference		$ 39,367
Series B redeemable convertible preferred stock
Redeemable convertible preferred stock, shares authorized		1,287,525
Redeemable convertible preferred stock, shares issued	0	1,287,525
Redeemable convertible preferred stock, shares outstanding	0	1,287,525
Redeemable convertible preferred stock, liquidation preference		21,031
Series C redeemable convertible preferred stock
Redeemable convertible preferred stock, shares authorized		3,428,572
Redeemable convertible preferred stock, shares issued	0	3,302,885
Redeemable convertible preferred stock, shares outstanding	0	3,302,885
Redeemable convertible preferred stock, liquidation preference		$ 97,203