Financial Derivatives (Schedule of Derivative Activity) (Details) - USD ($) $ in Thousands |
9 Months Ended | 12 Months Ended |
|---|---|---|
Sep. 30, 2019 |
Dec. 31, 2018 |
|
| Interest rate swaps | ||
| Derivative [Line Items] | ||
| Average Monthly Notional | $ 730,908 | $ 1,059,756 |
| TBA securities | ||
| Derivative [Line Items] | ||
| Average Monthly Notional | 1,087,157 | |
| Credit default swaps | ||
| Derivative [Line Items] | ||
| Average Monthly Notional | 410,213 | 566,805 |
| Total return swaps | ||
| Derivative [Line Items] | ||
| Average Monthly Notional | 39,779 | 53,603 |
| Futures | ||
| Derivative [Line Items] | ||
| Average Monthly Notional | 199,246 | 201,295 |
| Options | ||
| Derivative [Line Items] | ||
| Average Monthly Notional | 25,772 | 99,891 |
| Forwards | ||
| Derivative [Line Items] | ||
| Average Monthly Notional | 33,360 | $ 45,522 |
| Warrants | ||
| Derivative [Line Items] | ||
| Average Monthly Notional | $ 2,281 |