Summary of Significant Accounting Policies - Additional Information (Detail)
|
12 Months Ended |
|
Dec. 31, 2016
USD ($)
Segment
shares
|
Dec. 31, 2015
USD ($)
shares
|
Dec. 31, 2014
USD ($)
shares
|
| Accounting Policies [Line Items] |
|
|
|
| Restricted cash |
$ 251,000
|
$ 200,000
|
|
| Depreciation expense |
$ 997,000
|
817,000
|
$ 627,000
|
| Number of operating segments | Segment |
1
|
|
|
| Undelivered elements (training, installation, product and support services) |
$ 1,404,000
|
1,608,000
|
|
| Provision for sales returns |
210,000
|
210,000
|
|
| Extended warranty contracts |
$ 1,500,000
|
1,400,000
|
|
| Revenue recognition, percentage of fair value of trade-in exchange |
25.00%
|
|
|
| Advertising costs |
$ 351,000
|
929,000
|
543,000
|
| Compensation cost related to stock options |
3,065,000
|
3,350,000
|
$ 1,233,000
|
| Total unrecognized compensation cost |
$ 4,000,000
|
$ 4,400,000
|
|
| Unrecognized share based compensation cost to be recognized over weighted-average period |
2 years 6 months
|
|
|
| Outstanding stock options, restricted stock units and warrants excluded from diluted loss per share | shares |
20,537,000
|
17,371,000
|
13,606,000
|
| Executives |
|
|
|
| Accounting Policies [Line Items] |
|
|
|
| Fair value assumptions, forfeiture rate |
4.87%
|
|
|
| Employees |
|
|
|
| Accounting Policies [Line Items] |
|
|
|
| Fair value assumptions, forfeiture rate |
35.56%
|
|
|
| U S |
|
|
|
| Accounting Policies [Line Items] |
|
|
|
| Product warrant period |
2 years
|
2 years
|
2 years
|
| International |
|
|
|
| Accounting Policies [Line Items] |
|
|
|
| Product warrant period |
28 months
|
28 months
|
16 months
|