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Reinsurance (Cumulative Paid Claims) (Details) - USD ($) $ in Millions | Dec. 31, 2020 | Dec. 31, 2019 | Dec. 31, 2018 | Dec. 31, 2017 | Dec. 31, 2016
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Cumulative Paid Claims [Line Items] |  |  |  |  |
Cumulative Paid Claims | $ 140.0 |  |  |  |
Incident Year 2016 [Member] |  |  |  |  |
Cumulative Paid Claims [Line Items] |  |  |  |  |
Cumulative Paid Claims | 26.0 | $ 26.0 | $ 26.0 | $ 26.0 | $ 24.7
Incident Year 2017 [Member] |  |  |  |  |
Cumulative Paid Claims [Line Items] |  |  |  |  |
Cumulative Paid Claims | 22.6 | 22.6 | 22.5 | $ 21.3 |
Incident Year 2018 [Member] |  |  |  |  |
Cumulative Paid Claims [Line Items] |  |  |  |  |
Cumulative Paid Claims | 25.8 | 25.7 | $ 24.2 |  |
Incident Year 2019 [Member] |  |  |  |  |
Cumulative Paid Claims [Line Items] |  |  |  |  |
Cumulative Paid Claims | 30.2 | $ 28.3 |  |  |
Incident Year 2020 [Member] |  |  |  |  |
Cumulative Paid Claims [Line Items] |  |  |  |  |
Cumulative Paid Claims | $ 35.4 |  |  |  |

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