Commitments and Contingencies - Additional Information (Detail) $ in Millions		1 Months Ended				3 Months Ended	9 Months Ended
	Sep. 10, 2019 Patent	May 31, 2019 ft²	Jun. 30, 2018	Apr. 30, 2018 ft²	Jun. 30, 2014 ft²	Sep. 30, 2018 USD ($)	Sep. 30, 2019 USD ($) ft²	Sep. 30, 2018 USD ($)
Operating Leased Assets [Line Items]
Weighted-average remaining lease term							5 years 7 months 6 days
Weighted-average discount rate							7.70%
Rent expense | $						$ 0.5		$ 0.9
Number of patents infringes | Patent	2
Purchase commitments | $							$ 4.9
Lease Agreement | Oakwood Village, Ohio
Operating Leased Assets [Line Items]
Area of land							19,800
Lease agreement, expiration date							Oct. 31, 2021
Lease Agreement | Mountain View, California
Operating Leased Assets [Line Items]
Area of land				24,600	25,500
Lease agreement, expiration date			Jul. 31, 2025	Dec. 31, 2025	Nov. 30, 2019
Option to extend, description operating lease			extend the term of the lease agreement through July 2025
Option to extend, existence operating Lease			true
Lease commencement date				2018-12
Lease Agreement | Mountain View, California | Maximum
Operating Leased Assets [Line Items]
Lease agreement, renewal term				5 years
Sub-Lease Agreement | Denver, Colorado
Operating Leased Assets [Line Items]
Area of land		19,800
Lease agreement, expiration date		May 31, 2021
Lease commencement date		2019-06