Financial Derivatives (Narrative) (Details) - USD ($) $ in Millions |
3 Months Ended | 12 Months Ended |
|---|---|---|
Mar. 31, 2020 |
Dec. 31, 2019 |
|
| Derivative [Line Items] | ||
| Written credit derivative spread threshold | 20.00% | 20.00% |
| Upfront points on written credit derivative in excess of threshold | 57.0 | |
| Credit Default Swap, Selling Protection [Member] | ||
| Derivative [Line Items] | ||
| Credit risk derivative in excess of threshold, at fair value, net | $ (0.1) | $ (0.1) |
| Total net up-front payments received | $ (2.2) | $ (3.3) |
| Minimum | ||
| Derivative [Line Items] | ||
| Spread on written credit derivatives | 10.01% | 1.09% |
| Upfront points on written credit derivative in excess of threshold | 57.0 | |
| Maximum | ||
| Derivative [Line Items] | ||
| Spread on written credit derivatives | 100.11% | 44.00% |
| Upfront points on written credit derivative in excess of threshold | 85.2 |