Redeemable Convertible Preferred Stock - Series B Preferred Stock - (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Temporary Equity [Line Items]
Exchange of outstanding convertible notes and accrued interest into Series A redeemable convertible preferred stock and tranche rights			$ 2,929
Series B preferred stock
Temporary Equity [Line Items]
Proceeds from issuance of stock, net of issuance costs		$ 89,800
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 Excess Over Aggregate Fair Value	$ 5,000