Summary of Significant Accounting Policies - Additional Information (Details) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Concentration risk
Deferred revenue	$ 2,600,000	$ 2,900,000
Deferred cost of sales	900,000	1,100,000
Deferred income on shipments to distributors	1,720,000	1,827,000
Income Taxes
Interest and penalties on unrecognized tax benefits	0	0	$ 0
Recently Issued Pronouncement
Deferred income on shipments to distributors	1,720,000	$ 1,827,000
ASU 2014-09
Concentration risk
Deferred income on shipments to distributors	1,700,000
Recently Issued Pronouncement
Deferred income on shipments to distributors	1,700,000
ASU 2014-09 | Minimum
Recently Issued Pronouncement
Concessions and price protection credits offered to distributors	200,000
ASU 2014-09 | Maximum
Recently Issued Pronouncement
Concessions and price protection credits offered to distributors	$ 400,000