Organization and Summary of Significant Accounting Policies - Additional Information (Detail)	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2018 USD ($) Customer	Sep. 30, 2017 Customer	Sep. 30, 2018 USD ($) Customer	Sep. 30, 2017 Customer	Dec. 31, 2017 USD ($) Customer	Jan. 01, 2018 USD ($)
Accounting Policies [Line Items]
Number of major customer represented stated percentage of total net revenue | Customer	0	0	0	0
Number of customers who accounted for 10% or more of accounts receivable balance | Customer			0		0
Concentration Risk, Customer			No customer represented more than 10% of net revenue for either of the three or nine months ended September 30, 2018 or 2017. No customer represented 10% or more of the Company’s accounts receivable balance at September 30, 2018 or December 31, 2017.
Capitalized software development costs	$ 386,000		$ 386,000
Software development costs capitalized in period			0		$ 401,000
Accumulated deficit	(404,983,000)		(404,983,000)		(399,647,000)
Deferred Revenue	$ 2,265,000		$ 2,265,000		$ 900,000
Topic 606
Accounting Policies [Line Items]
Accumulated deficit						$ (399,645,000)
Capitalized incremental sales commision costs or other costs						0
Topic 606 | On Delivery
Accounting Policies [Line Items]
Percentage of revenue recognized	94.00%		95.00%
Topic 606 | Over Time
Accounting Policies [Line Items]
Percentage of revenue recognized	6.00%		5.00%
Topic 606 | Adjustments
Accounting Policies [Line Items]
Accumulated deficit						2,000
Deferred Revenue						$ (2,000)
Minimum
Accounting Policies [Line Items]
Estimated useful lives of intangible asset			4 years
Maximum
Accounting Policies [Line Items]
Estimated useful lives of intangible asset			12 years