Commitments and Contingencies - Operating Leases (Details)	Nov. 02, 2015 USD ($) ft²	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)
Headquarters Facility, Amendment to Commercial Sublease [Member]
Operating Leased Assets [Line Items]
Lease term	6 months
Base monthly rent during the extension period	$ 47,000
Lease Expiration Date	Aug. 31, 2016
Headquarters Facility in Santa Clara [Member]
Operating Leased Assets [Line Items]
Base monthly rent during the extension period	$ 93,000
Area leased (in sqft) | ft²	34,000
Lease Expiration Date	Jul. 31, 2023
Optional Lease Extension Term	5 years
Annual increase of monthly rent after February 27, 2017	3.00%
Reimbursement for out-of-pocket costs associated with any tenant improvements	$ 2,500,000
Lease incentive obligation		$ 2,000,000	$ 2,400,000
Lease incentive obligation, current		400,000	400,000
Lease incentive obligation, noncurrent		$ 1,600,000	$ 2,000,000