Consolidated Balance Sheets (Parenthetical) - USD ($)	Sep. 30, 2018	Dec. 31, 2017
Accounts receivable, allowances	$ 287,000	$ 438,000
Convertible preferred stock, par value (in dollars per share)	$ 0.0001	$ 0.0001
Convertible preferred stock, shares authorized (in shares)	5,000,000	0
Convertible preferred stock, shares issued (in shares)	0	0
Convertible preferred stock, shares outstanding (in shares)	0	0
Common stock, par value (in dollars per share)	$ 0.0001	$ 0.0001
Common stock, shares authorized (in shares)	190,000,000	190,000,000
Common stock, shares issued (in shares)	36,356,000	2,979,000
Common stock, shares outstanding (in shares)	36,356,000	2,979,000
Convertible preferred stock
Convertible preferred stock, par value (in dollars per share)	$ 0.0001	$ 0.0001
Convertible preferred stock, shares authorized (in shares)	0	129,478,000
Convertible preferred stock, shares issued (in shares)	0	24,642,000
Convertible preferred stock, shares outstanding (in shares)	0	24,642,000
Convertible preferred stock, liquidation preference	$ 0	$ 148,454,000