Stockholders' Equity (Deficit) (Details 2) - USD ($)	1 Months Ended	3 Months Ended		9 Months Ended		12 Months Ended
	Jan. 31, 2015	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014	Dec. 31, 2014
Weighted Average Exercise Price
Share based compensation expense		$ 1,211,000	$ 192,000	$ 3,691,000	$ 509,000
2015 Plan
Stock options
Shares reserved for issuance	1,320,000
Maximum annual increase in shares available for issuance (in shares)				1,690,000
Maximum annual increase in shares available for issuance, percentage of outstanding shares				5.00%
Stock options
Stock options
Vesting period				4 years
Expiration term				10 years
Shares available for grant
Balance at the beginning of the period (in shares)	21,705			21,705
Additional shares reserved (in shares)		1,320,000		1,320,000
Granted (in shares)				(261,288)
Cancelled (in shares)				215,177
Balance at the end of the period (in shares)		1,295,594		1,295,594		21,705
Options outstanding
Balance outstanding at the beginning of the period (in shares)	3,010,373			3,010,373
Granted (in shares)				(261,288)
Exercised (in shares)				(277)
Cancelled (in shares)				(215,177)
Balance outstanding at the end of the period (in shares)		3,056,207		3,056,207		3,010,373
Weighted Average Exercise Price
Balance at the beginning of the period (in dollars per share)	$ 5.78			$ 5.78
Granted (in dollars per shares)				12.83
Exercised (in dollars per shares)				4.50
Cancelled (in dollars per share)				9.54
Balance at the end of the period (in dollars per share)		$ 6.12		$ 6.12		$ 5.78
Aggregate Intrinsic Value		$ 27,142,000		$ 27,142,000		$ 13,188,000
Weighted-average grant date fair value of options granted				$ 6.56	$ 0.13
Aggregate intrinsic value of options outstanding and vested		$ 630,000		$ 630,000
Aggregate intrinsic value of options exercised				$ 0	$ 0
Shares vested				252,016		201,018
Weighted average exercise price of options vested		$ 14.31		$ 14.31		$ 5.38
Weighted average remaining contractual term				6 years 6 months 18 days		7 years 11 days
Common stock remained reserved for issuance		1,320,000		1,320,000
Stock options | Minimum
Stock options
Exercise price as percentage of fair value of shares				100.00%
Stock options | Minimum | Stockholder with more than 10% voting power
Stock options
Exercise price as percentage of fair value of shares				110.00%
2015 Employee Stock Purchase Plan
Stock options
Shares reserved for issuance	500,000
Maximum annual increase in shares available for issuance (in shares)				493,000
Maximum annual increase in shares available for issuance, percentage of outstanding shares				1.50%
Shares available for grant
Additional shares reserved (in shares)		468,000		468,000
Weighted Average Exercise Price
Maximum percentage of fair value to be considered under the plan	85.00%
Common stock remained reserved for issuance		468,000		468,000
Share based compensation expense		$ 45,000		$ 112,000