Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Statement of Financial Position [Abstract]
Accounts receivable, allowances	$ 482	$ 438
Convertible preferred stock, par value (in dollars per share)	$ 0.0001	$ 0.0001
Convertible preferred stock, shares authorized (in shares)	129,478,000	129,478,000
Convertible preferred stock, shares issued (in shares)	24,642,000	24,642,000
Convertible preferred stock, shares outstanding (in shares)	24,642,000	24,642,000
Convertible preferred stock, liquidation preference	$ 148,454	$ 148,454
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)	3,056,000	2,979,000
Common stock, shares outstanding (in shares)	3,056,000	2,979,000