| Schedule of Additional Balance Sheet Components | The components of certain balance sheet amounts are as follows (in thousands): 
|  |  
|  |  |  |  |  |  |  |  |  
|   | December 31, |  
|   | 2018 |   | 2017 |  
| Cash and cash equivalents: |   |   |   |  
| Cash | $ | 47,323 | 
 |   | $ | 61,703 | 
 |  
| Cash equivalents | 85,330 | 
 |   | 73,608 | 
 |  
|   | 132,653 | 
 |   | 135,311 | 
 |  
| Restricted cash | 2,998 | 
 |   | 3,167 | 
 |  
|   | $ | 135,651 | 
 |   | $ | 138,478 | 
 |  
|   |   |   |   |  
| Inventories: |   |   |   |  
| Finished goods | $ | 11,171 | 
 |   | $ | 7,779 | 
 |  
| Raw materials | 1,145 | 
 |   | 799 | 
 |  
| Reserve for obsolescence | (151 | ) |   | (180 | ) |  
|   | $ | 12,165 | 
 |   | $ | 8,398 | 
 |  
| Property and equipment: |   |   |   |  
| Office equipment | $ | 537 | 
 |   | $ | 530 | 
 |  
| Office software | 918 | 
 |   | 916 | 
 |  
| Machinery | 29 | 
 |   | 30 | 
 |  
| Furniture and fixtures | 319 | 
 |   | 276 | 
 |  
| Leasehold improvements | 1,022 | 
 |   | 957 | 
 |  
| Construction in progress (including internal-use software development costs) | 19 | 
 |   | 10 | 
 |  
| Property and equipment, at cost | 2,844 | 
 |   | 2,719 | 
 |  
| Accumulated depreciation and amortization | (1,910 | ) |   | (1,570 | ) |  
|   | $ | 934 | 
 |   | $ | 1,149 | 
 |  
| Other accrued expenses: |   |   |   |  
| Sales returns | $ | 801 | 
 |   | $ | 614 | 
 |  
| Employee-related expense | 4,051 | 
 |   | 5,568 | 
 |  
| Warehousing, inventory-related and other | 1,269 | 
 |   | 1,423 | 
 |  
|   | $ | 6,121 | 
 |   | $ | 7,605 | 
 |  
| Deferred revenue: |   | 
 |   |   | 
 |  
| Unshipped product | $ | 4,574 | 
 |   | $ | 2,411 | 
 |  
| Auto ship advances | 1,876 | 
 |   | 1,665 | 
 |  
| Other | 345 | 
 |   | 379 | 
 |  
|   | $ | 6,795 | 
 |   | $ | 4,455 | 
 |  |