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Goodwill and Other Intangible Assets - Fair Value of Goodwill and Intangible Assets (Details) - USD ($) $ in Millions | Sep. 30, 2019 | Jun. 28, 2019 | Apr. 04, 2019 | Apr. 01, 2019 | Mar. 12, 2019 | Dec. 03, 2018 | May 18, 2018 | May 11, 2018
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NSM Holding Co LLC |  |  |  |  |  |  |  |
Finite-Lived Intangible Assets [Line Items] |  |  |  |  |  |  |  |
Goodwill and intangible assets acquired | $ 653.0 |  |  |  |  |  |  |
Renewal Rights |  |  |  |  |  |  |  |
Finite-Lived Intangible Assets [Line Items] |  |  |  |  |  |  |  |
Goodwill and intangible assets acquired |  | $ 82.5 |  |  |  |  |  |
NSM Holding Co LLC |  |  |  |  |  |  |  |
Finite-Lived Intangible Assets [Line Items] |  |  |  |  |  |  |  |
Goodwill and intangible assets acquired |  |  |  |  |  |  |  | $ 383.0
Fresh Insurance Services Group Limited |  |  |  |  |  |  |  |
Finite-Lived Intangible Assets [Line Items] |  |  |  |  |  |  |  |
Goodwill and intangible assets acquired |  |  |  |  |  |  | $ 54.6 |
KBK Insurance Group, Inc. & KBK Premium Services, Inc. |  |  |  |  |  |  |  |
Finite-Lived Intangible Assets [Line Items] |  |  |  |  |  |  |  |
Goodwill and intangible assets acquired |  |  |  |  |  | $ 65.3 |  |
Embrace Pet Insurance |  |  |  |  |  |  |  |
Finite-Lived Intangible Assets [Line Items] |  |  |  |  |  |  |  |
Goodwill and intangible assets acquired |  |  |  | $ 67.6 |  |  |  |
Kudu |  |  |  |  |  |  |  |
Finite-Lived Intangible Assets [Line Items] |  |  |  |  |  |  |  |
Goodwill and intangible assets acquired |  |  | $ 9.8 |  |  |  |  |
Other Operations |  |  |  |  |  |  |  |
Finite-Lived Intangible Assets [Line Items] |  |  |  |  |  |  |  |
Goodwill and intangible assets acquired |  |  |  |  | $ 22.6 |  |  |
Other Assets | Embrace Pet Insurance |  |  |  |  |  |  |  |
Finite-Lived Intangible Assets [Line Items] |  |  |  |  |  |  |  |
Software |  |  |  | $ 3.4 |  |  |  |

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