Financial Derivatives (Schedule of Credit Derivatives) (Details) - USD ($) $ in Thousands |
Mar. 31, 2019 |
Dec. 31, 2018 |
|---|---|---|
| Credit Default Swap, Selling Protection [Member] | ||
| Credit Derivatives [Line Items] | ||
| Fair Value of Written Credit Derivatives, Net | $ 2,598 | $ (4,339) |
| Notional value | 89,230 | 98,586 |
| Credit Default Swap, Buying Protection [Member] | ||
| Credit Derivatives [Line Items] | ||
| Fair Value of Written Credit Derivatives, Net | (167) | (284) |
| Notional value | $ 13,153 | $ 41,134 |