Redeemable Convertible Preferred Stock and Stockholders' Equity (Deficit) - USD ($) $ in Thousands	Redeemable Convertible Preferred Stock	Redeemable Convertible Preferred Stock Series A Preferred Stock	Redeemable Convertible Preferred Stock Series B Preferred Stock Issuance Number #1	Redeemable Convertible Preferred Stock Series B Preferred Stock	Redeemable Convertible Preferred Stock Series B	Common Stock IPO	Common Stock	Additional Paid-in Capital IPO	Additional Paid-in Capital	Accumulated Other Comprehensive Loss	Accumulated Deficit	IPO	Total
Stockholders' Equity, Begining Balance at Dec. 31, 2013											$ (3,833)		$ (3,833)
Shares, Outstanding, Beginning Balance at Dec. 31, 2013							2,352
Issuance of common stock for services							$ 1		$ 251				252
Issuance of common stock for services							494,118
Initial issuance of Series A redeemable convertible preferred stock, including exchange of convertible notes payable and net of tranche rights and issuance costs		$ 3,878
Initial issuance of Series A redeemable convertible preferred stock, including exchange of convertible notes payable and net of tranche rights and issuance costs ( in shares)		6,500,000
Issuance of preferred stock, net of discount and issuance costs		$ 18,491
Reclassification of tranche rights upon issuance of Series A redeemable convertible preferred stock		(1,756)
Net loss											(16,317)		(16,317)
Vesting of restricted common stock									9				9
Vesting of restricted common stock (in shares)							318,364
Adjustments to Additional Paid in Capital, Share-based Compensation, Requisite Service Period Recognition									425				425
Stock-based compensation expense									425				425
Accretion of redeemable convertible preferred stock to redemption value (Preferred Stock)		1,366
Accretion of redeemable convertible preferred stock to redemption value									685		681		1,366
Stockholders' Equity, Ending Balance at Dec. 31, 2014		$ 21,979					$ 1				(20,831)		(20,830)
Shares, Outstanding, Ending Balance at Dec. 31, 2014		25,000,000					814,834
Issuance of preferred stock, net of discount and issuance costs (in shares)	25,000,000	18,500,000
Issuance of common stock						$ 6		$ 72,948				$ 72,954
Issuance of common stock (in shares)						5,750,000
Issuance of preferred stock, net of discount and issuance costs		$ 19,999	$ 84,780
Reclassification of tranche rights upon issuance of Series A redeemable convertible preferred stock		16,055
Conversion of redeemable convertible preferred stock to common stock		$ (60,182)		$ (90,005)			$ 18		144,675		5,494		150,187
Conversion of redeemable convertible preferred stock to common stock (common stock shares)							17,647,054
Conversion of redeemable convertible preferred stock to common stock (preferred stock shares)		(45,000,000)		(30,000,001)
Net loss											(29,672)		(29,672)
Vesting of restricted common stock									22				22
Vesting of restricted common stock (in shares)							717,747
Adjustments to Additional Paid in Capital, Share-based Compensation, Requisite Service Period Recognition									4,027				4,027
Stock-based compensation expense									4,027				4,027
Unrealized loss on available for-sale securities										$ (251)			(251)
Accretion of redeemable convertible preferred stock to redemption value (Preferred Stock)		$ 2,149		$ 5,225
Accretion of redeemable convertible preferred stock to redemption value									2,560		4,813		7,373
Exercises of vested stock options									10				10
Exercises of vested stock options (in shares)							1,344
Stockholders' Equity, Ending Balance at Dec. 31, 2015							$ 25		$ 219,122	$ (251)	$ (49,822)		$ 169,074
Shares, Outstanding, Ending Balance at Dec. 31, 2015							24,930,979
Issuance of preferred stock, net of discount and issuance costs (in shares)	0	20,000,000	30,000,001		30,000,001