Financial Derivatives (Narrative) (Details) - USD ($) $ in Millions |
12 Months Ended | ||
|---|---|---|---|
Dec. 31, 2020 |
Dec. 31, 2019 |
Dec. 31, 2018 |
|
| Derivative [Line Items] | |||
| Written credit derivative spread threshold | 20.00% | 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) | $ (1.0) |
| Total net up-front payments received | $ (2.0) | $ (3.3) | $ (2.0) |
| Minimum | |||
| Derivative [Line Items] | |||
| Spread on written credit derivatives | 4.00% | 1.09% | 4.26% |
| Upfront points on written credit derivative in excess of threshold | 56.2 | 36.9 | |
| Maximum | |||
| Derivative [Line Items] | |||
| Spread on written credit derivatives | 27.48% | 44.00% | 81.51% |
| Upfront points on written credit derivative in excess of threshold | 85.2 | 75.2 | |