Notes Payable-Related Party (Details) - USD ($) $ in Thousands			3 Months Ended
	Jan. 20, 2017	Jan. 13, 2017	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2016	Dec. 31, 2014
Proceeds from promissory notes
Interest expense-related party				$ 121
Proceeds from promissory notes				750
Conversion of notes payable - related party and accrued interest into common stock				31,145
Conversion of notes payable - related party and accrued interest into common stock | Common Stock
Proceeds from promissory notes
Shares issued on conversion of notes payable and related accrued interest	1,950,768
Convertible Promissory notes | Convertible promissory note executed with stockholder | Stockholder
Proceeds from promissory notes
Note interest rate (as a percent)						8.00%
Promissory notes payable outstanding					$ 29,000
Accrued interest expense					$ 1,274
Interest expense-related party			$ 0	$ 121
Proceeds from promissory notes		$ 750
Convertible Promissory notes | Convertible promissory note executed with stockholder | Stockholder | Conversion of notes payable - related party and accrued interest into common stock
Proceeds from promissory notes
Conversion of notes payable - related party and accrued interest into common stock	$ 31,145