Revenue from Contracts with Customers - Aditional Information (Detail) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017	Dec. 31, 2017
Revenue from Contracts with Customers [Line Items]
Adjustment to deferred revenue and accumulated deficit			$ 5,703,000
Deferred revenue	$ 887,000		887,000		$ 6,141,000
Sales and marketing	563,000	$ 410,000	$ 982,000	$ 788,000
Minimum [Member]
Revenue from Contracts with Customers [Line Items]
Engagement term			3 months
Maximum [Member]
Revenue from Contracts with Customers [Line Items]
Engagement term			6 months
Product [Member]
Revenue from Contracts with Customers [Line Items]
Adjustment to deferred revenue and accumulated deficit			$ 5,703,000
Deferred revenue	255,000		255,000		5,888,000
Service [Member]
Revenue from Contracts with Customers [Line Items]
Deferred revenue	632,000		632,000		$ 253,000
Topic 606 [Member]
Revenue from Contracts with Customers [Line Items]
Contract cost			200,000
Topic 606 [Member] | Prepaid Expenses and Other Current Assets [Member]
Revenue from Contracts with Customers [Line Items]
Contract cost			200,000
Topic 606 [Member] | License [Member]
Revenue from Contracts with Customers [Line Items]
Remaining performance obligation	0		0
Upfront consideration received			300,000
Accordance with Topic 605 [Member] | Topic 606 [Member] | Product [Member]
Revenue from Contracts with Customers [Line Items]
Revenue	10,300,000		19,000,000
Deferred revenue	6,400,000		6,400,000
Accordance with Topic 605 [Member] | Topic 606 [Member] | Service [Member]
Revenue from Contracts with Customers [Line Items]
Sales and marketing	$ 39,000		$ 11,000