Description of Business and Summary of Significant Accounting Policies (Impairment of Long-Lived Assets and Goodwill) (Details) - USD ($) |
12 Months Ended | ||
|---|---|---|---|
Dec. 31, 2018 |
Dec. 31, 2017 |
Dec. 31, 2016 |
|
| Description of Business and Summary of Significant Accounting Policies | |||
| Impairment of long lived assets | $ 0 | $ 0 | $ 0 |
| Impairment of goodwill | $ 0 | $ 0 | $ 0 |