Summary of Significant Accounting Policies (Estimated Fair Value and Carrying Value of Notes) (Details) - USD ($) $ in Thousands |
Sep. 30, 2019 |
Dec. 31, 2018 |
|---|---|---|
| Estimated Fair Value [Member] | ||
| Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items] | ||
| Notes payable | $ 16,069 | $ 15,915 |
| Carrying Value [Member] | ||
| Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items] | ||
| Notes payable | $ 15,546 | $ 14,659 |