Stock-based Compensation (Schedule of Nonvested Shares of Restricted Common Stock Activity) (Details) - Class A shares [Member] - 2014 Restricted Share Plan [Member] - Restricted Stock [Member] - shares |
12 Months Ended | ||
|---|---|---|---|
Jul. 24, 2018 |
Jul. 20, 2018 |
Dec. 31, 2018 |
|
| Summary of Restricted Common Stock Activity, Nonvested, Number of Shares [Roll Forward] | |||
| Beginning balance (in shares) | 22,500 | ||
| Vested (in shares) | (9,000) | ||
| Granted (in shares) | 3,000 | 9,000 | 12,000 |
| Ending balance (in shares) | 25,500 |