Summary of Significant Accounting Policies - Narrative (Details) |
12 Months Ended | ||
|---|---|---|---|
|
Dec. 31, 2015
USD ($)
segment
|
Dec. 31, 2014
USD ($)
|
Dec. 31, 2013
USD ($)
|
|
| Basis of Presentation | |||
| Number of operating segments | segment | 1 | ||
| Impairments | $ 0 | $ 0 | $ 0 |
| Carperks | |||
| Basis of Presentation | |||
| Payments made upon achievement of sales milestones | $ 1,900,000 | ||