Consolidated Statements of Preferred Stock and Stockholders' Equity (Deficit) - USD ($) $ in Thousands	Total	Series A-1 Redeemable Convertible Preferred Stock [Member]	Convertible Preferred Stock [Member]	Initial Public Offering [Member]	Initial Public Offering [Member] Series A-1 Redeemable Convertible Preferred Stock [Member]	Initial Public Offering [Member] Convertible Preferred Stock [Member]	Special Voting Stock [Member]	Common Stock [Member]	Common Stock [Member] Initial Public Offering [Member]	Additional Paid-in Capital [Member]	Additional Paid-in Capital [Member] Initial Public Offering [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Accumulated Deficit [Member]
Stock-based compensation	$ 1,388									$ 1,388
Temporary equity, Beginning balance at Dec. 31, 2012		$ 52,274	$ 5,450
Beginning Balance at Dec. 31, 2012	(28,416)						$ 1			64,166		$ 9	$ (92,591)
Temporary equity, Beginning balance, Shares at Dec. 31, 2012		7,761,608	809,205
Beginning Balance, Shares at Dec. 31, 2012								58,945
Change in fair value of redeemable non-controlling interest	(3,105)									(3,105)
Share exchange related to non-controlling interest and special voting stock		$ 7,824					(1)
Share exchange related to non-controlling interest and special voting stock, Temporary equity, Shares		714,427
Deemed dividend	(856)									(856)
Temporary equity, Ending balance at Dec. 31, 2013		$ 60,098
Temporary equity, Ending balance, Shares at Dec. 31, 2013		8,476,035,000	809,205,000
Consolidated net loss	(20,091)												(20,091)
Net loss attributable to redeemable non-controlling interest	96												96
Unrealized (loss) gain on investments	(7)											(7)
Ending Balance at Dec. 31, 2013	(50,991)									61,593		2	(112,586)
Ending Balance, Shares at Dec. 31, 2013								58,945
Impact of initial public offering
Stock-based compensation	1,388									1,388
Consolidated net loss	(20,091)												(20,091)
Unrealized (loss) gain on investments	(7)											(7)
Ending Balance at Dec. 31, 2013	(50,991)									61,593		2	(112,586)
Stock-based compensation	3,319									3,319
Conversion of convertible securities into stock, Temporary equity value				$ 1,117	$ (60,098)	$ (5,450)					$ 1,117
Common stock issuance upon exercise of warrants	143									143
Conversion of convertible securities into stock, Temporary equity shares					(8,476,035)	(809,205)
Common stock issuance upon exercise of warrants, Shares								1,698,000
Exercise of stock options	407									407
Exercise of stock options, Shares								22,681
Consolidated net loss	(33,853)												(33,853)
Unrealized (loss) gain on investments	(10)											(10)
Ending Balance at Dec. 31, 2014	$ 72,104							$ 2		218,549		(8)	(146,439)
Ending Balance, Shares at Dec. 31, 2014	1,566,045							1,566,045
Impact of initial public offering
Common stock issuance upon exercise of warrants	$ 143									143
Common stock issuance upon exercise of warrants, Shares								1,698,000
Public offering of common stock, net	40,689			44,258					$ 1	40,689	44,257
Public offering of common stock, net, Shares								306,666,000	421,666
Stock-based compensation	3,319									3,319
Conversion of convertible notes into common stock				1,117	$ (60,098)	$ (5,450)					1,117
Exercise of stock options	407									407
Conversion of convertible notes into common stock, shares									9,309,000
Exercise of stock options, Shares								22,681
Conversion of convertible securities into stock				65,548					$ 1		65,547
Issuance of common stock under employee stock purchase plan	178									178
Conversion of convertible securities into stock, Shares									743,412,000
Issuance of common stock under employee stock purchase plan, Shares								1,668
Warrant liability reclassification				$ 1,299							$ 1,299
Consolidated net loss	(33,853)												(33,853)
Unrealized (loss) gain on investments	(10)											(10)
Ending Balance at Dec. 31, 2014	72,104							$ 2		218,549		(8)	(146,439)
Stock-based compensation	3,028									3,028
Common stock issuance upon exercise of warrants, Shares								2,818
Exercise of stock options	$ 826									826
Exercise of stock options, Shares	27,815							27,815
Stock issued upon RSU release	$ 0						$ 0	$ 0		0		0	0
Stock issued upon RSU release, Share								275
Consolidated net loss	(44,413)												(44,413)
Unrealized (loss) gain on investments	8											8
Ending Balance at Dec. 31, 2015	$ 31,553							$ 2		222,403			(190,852)
Ending Balance, Shares at Dec. 31, 2015	1,596,953							1,596,953
Impact of initial public offering
Common stock issuance upon exercise of warrants, Shares								2,818
Stock-based compensation	$ 3,028									3,028
Exercise of stock options	$ 826									826
Exercise of stock options, Shares	27,815							27,815
Consolidated net loss	$ (44,413)												(44,413)
Unrealized (loss) gain on investments	8											$ 8
Ending Balance at Dec. 31, 2015	$ 31,553							$ 2		$ 222,403			$ (190,852)