Stockholders' Equity - Warrant (Details) - USD ($)		12 Months Ended
	Jun. 19, 2017	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Jul. 25, 2017	Jun. 30, 2017	Jun. 29, 2017
Class of Warrant or Right [Line Items]
Common stock, par value (in dollars per share)		$ 0.0001	$ 0.0001			$ 0.0001
Common stock, shares issued (in shares)		27,707,328	23,102,728
Series A-1 warrant liability	$ 3,300,000	$ 3,313,000	$ 0	$ 0
Change in fair value of warrant liability		(2,217,000)	0	$ 0
Aggregate intrinsic value of the warrant		0
Series A Preferred Stock
Class of Warrant or Right [Line Items]
Value of shares redeemed		$ 13,800,000	$ 2,800,000
Number of shares redeemed (in shares)		83,502	18,498
Reduction in the original recorded value of preferred stock		$ 8,400,000	$ 1,800,000
Reduction in the accretive value of the preferred stock		$ 5,400,000	$ 1,000,000
Common Stock Warrant
Class of Warrant or Right [Line Items]
Common stock, par value (in dollars per share)		$ 0.0001
Right to acquire variable amount of common stock, term	15 months
Common Stock Warrant | Soryn HLDR
Class of Warrant or Right [Line Items]
Exercise price (in dollars per share)	$ 3.18	$ 3.18
Term of warrant	3 years	2 years 6 months
Common Stock | Common Stock Warrant | Soryn HLDR
Class of Warrant or Right [Line Items]
Common stock warrant purchased (in shares)	2,355,506					2,400,000	2,000,000
Common stock, shares issued (in shares)	2,000,000				46,370	309,136
Series A-1 warrant liability		$ 1,100,000
Change in fair value of warrant liability		$ 2,200,000