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Reinsurance (Cumulative Paid Claims) (Details) - USD ($) $ in Millions | Dec. 31, 2018 | Dec. 31, 2017 | Dec. 31, 2016 | Dec. 31, 2015 | Dec. 31, 2014
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Cumulative Paid Claims [Line Items] |  |  |  |  |
Cumulative Paid Claims | $ 146.0 |  |  |  |
Incident Year 2014 [Member] |  |  |  |  |
Cumulative Paid Claims [Line Items] |  |  |  |  |
Cumulative Paid Claims | 39.9 | $ 39.9 | $ 39.9 | $ 39.9 | $ 38.3
Incident Year 2015 [Member] |  |  |  |  |
Cumulative Paid Claims [Line Items] |  |  |  |  |
Cumulative Paid Claims | 33.4 | 33.4 | 33.4 | $ 31.9 |
Incident Year 2016 [Member] |  |  |  |  |
Cumulative Paid Claims [Line Items] |  |  |  |  |
Cumulative Paid Claims | 26.0 | 26.0 | $ 24.7 |  |
Incident Year 2017 [Member] |  |  |  |  |
Cumulative Paid Claims [Line Items] |  |  |  |  |
Cumulative Paid Claims | 22.5 | $ 21.3 |  |  |
Incident Year 2018 [Member] |  |  |  |  |
Cumulative Paid Claims [Line Items] |  |  |  |  |
Cumulative Paid Claims | $ 24.2 |  |  |  |

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