Significant Balance Sheet Components - Property and Equipment (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Property Plant And Equipment [Line Items]
Total property and equipment	$ 24,303	$ 23,426
Accumulated depreciation and amortization	(18,774)	(16,380)
Total property and equipment-net	5,529	7,046
Computers and appliances
Property Plant And Equipment [Line Items]
Total property and equipment	14,218	13,517
Purchased software
Property Plant And Equipment [Line Items]
Total property and equipment	4,886	4,711
Furniture and fixtures
Property Plant And Equipment [Line Items]
Total property and equipment	1,799	1,695
Leasehold improvements
Property Plant And Equipment [Line Items]
Total property and equipment	$ 3,400	$ 3,503