Balance Sheet Components - Allowance for Doubtful Accounts (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Allowance for doubtful accounts
Beginning balance	$ 1,788	$ 2,000	$ 1,890
Provision for estimated bad debts	1,141	(41)	143
Write offs	(10)	(171)	(33)
Ending balance	$ 2,919	$ 1,788	$ 2,000