Significant Balance Sheet Components - Accounts Receivable, Net (Details) - USD ($)	Sep. 30, 2019	Dec. 31, 2018
Accounts Receivable, Net
Allowance for doubtful accounts	$ (391,000)	$ (425,000)
Accounts receivable, net	44,564,000	60,994,000
Billed
Accounts Receivable, Net
Accounts receivable	42,749,000	60,037,000
Unbilled
Accounts Receivable, Net
Accounts receivable	$ 2,206,000	$ 1,382,000