Segment Information - Narrative (Details) |
3 Months Ended |
|---|---|
|
Mar. 31, 2018
vehicle / policy
vehicle
segment
| |
| Segment Reporting [Abstract] | |
| Number of operating segments | segment | 3 |
| Number of vehicles in fleet in target businesses (or fewer) | vehicle | 10 |
| Average vehicles per policy | vehicle / policy | 1.9 |