Balance Sheet Components - Other Assets (Details) - USD ($) $ in Thousands		1 Months Ended	3 Months Ended	9 Months Ended
	Aug. 08, 2017	Apr. 30, 2016	Sep. 30, 2018	Sep. 30, 2018	Dec. 31, 2017	Aug. 14, 2017
Balance Sheet Components [Line Items]
Agreement term		4 years
Total consideration		$ 3,200
Deferred costs included in other long-term assets			$ 1,200	$ 1,200	$ 1,800
Amortization of deferred costs			$ 200	$ 600
Common stock, shares issued			61,673,000	61,673,000	54,040,000
Debt discount			$ 600	$ 600
Noncurrent assets			3,446	3,446	$ 3,979
2017 Term Loan
Balance Sheet Components [Line Items]
Common stock, shares issued						300,000
Payments of debt issuance costs	$ 300
Debt discount	2,700
Debt instrument, fee amount	2,400
Remaining borrowing capacity	25,000
2017 Term Loan | Direct reduction from outstanding debt balance
Balance Sheet Components [Line Items]
Debt instrument, fee amount	2,000		1,700	1,700
2017 Term Loan | Noncurrent assets
Balance Sheet Components [Line Items]
Debt instrument, fee amount	$ 700
Evercord | Storage services
Balance Sheet Components [Line Items]
Noncurrent assets			$ 300	$ 300