Redeemable Convertible Preferred Stock - Series A Preferred Stock- Series A Preferred Stock- (Details) - USD ($) $ / shares in Units, $ in Thousands		1 Months Ended	12 Months Ended
	Nov. 16, 2015	Nov. 30, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Temporary Equity [Line Items]
Shares issued upon conversion of redeemable convertible preferred stock	17,647,054	17,647,054
Exchange of outstanding convertible notes and accrued interest into Series A redeemable convertible preferred stock and tranche rights					$ 2,929
Redeemable Convertible Preferred Stock Series A
Temporary Equity [Line Items]
Preferred Stock, Shares Authorized				45,000,000	45,000,000
Redeemable convertible preferred stock, issued (in shares)				20,000,000	18,500,000
Price per share				$ 1.00	$ 1.00
Proceeds from issuance of stock, net of issuance costs and exchange of outstanding convertible notes			$ 42,000
Proceeds from issuance of stock, net of issuance costs			32
Exchange of outstanding convertible notes and accrued interest into Series A redeemable convertible preferred stock and tranche rights			$ 2,900
Redeemable Convertible Preferred Stock Series B
Temporary Equity [Line Items]
Redeemable convertible preferred stock, issued (in shares)				30,000,001
Price per share			$ 3.00
Issuance costs			$ 200
Discount recorded against proceeds received for temporary equity related to payment in excess over fair value			$ 5,000
Redeemable Preferred Stock
Temporary Equity [Line Items]
Preferred Stock, Shares Authorized			5,000,000	5,000,000
Common Stock
Temporary Equity [Line Items]
Shares issued upon conversion of redeemable convertible preferred stock				17,647,054