Balance Sheet Components - Accounts Receivable and Allowance (Details) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2018
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Allowance for doubtful accounts	$ 600,000		$ 600,000		$ 200,000
Bad debt expense	$ 400,000	$ 0	861,000	$ 909,000
Write-off of uncollectible accounts receivable			$ 400,000	$ 900,000