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Goodwill and Other Intangible Assets (Goodwill and Intangible Assets Rollforward) (Details) - USD ($) $ in Millions | 12 Months Ended
--- | ---
Dec. 31, 2019 | Dec. 31, 2018 | Dec. 31, 2017
Goodwill [Roll Forward] |  |  |
Beginning balance | $ 379.9 |  |
Ending balance | 394.7 | $ 379.9 |
Finite-lived Intangible Assets [Roll Forward] |  |  |
Amortization | (21.8) | (18.8) | $ (10.7)
Goodwill and Intangible Assets [Roll Forward] |  |  |
Purchases of consolidated subsidiaries, net of cash acquired | 258.0 | 295.2 | 27.6
Goodwill, impairment loss | 7.6 |  |
Other Intangible Assets |  |  |
Goodwill [Roll Forward] |  |  |
Measurement period adjustments(5) | 26.8 |  |
Measurement period adjustments | 5.9 |  |
Finite-lived Intangible Assets [Roll Forward] |  |  |
Beginning balance | 157.6 | 36.2 |
Acquisitions of businesses | 34.6 | 140.9 |
Foreign currency translation | 0.7 | (0.7) |
Amortization | (21.8) | (18.8) |
Ending balance | 260.0 | 157.6 | 36.2
Goodwill and Intangible Assets [Roll Forward] |  |  |
Impairments | 2.8 |  |
Renewal Rights |  |  |
Finite-lived Intangible Assets [Roll Forward] |  |  |
Acquisitions of businesses | 82.5 |  |
Goodwill |  |  |
Goodwill [Roll Forward] |  |  |
Beginning balance | 379.9 | 25.9 |
Acquisitions of businesses | 64.8 | 356.5 |
Dispositions of businesses (2) | (18.3) |  |
Measurement period adjustments(5) | (26.8) |  |
Write-off | (7.6) |  |
Measurement period adjustments | 0.9 |  |
Foreign currency translation | 1.8 | (2.5) |
Ending balance | 394.7 | 379.9 | 25.9
Intangible Asset and Goodwill |  |  |
Goodwill [Roll Forward] |  |  |
Dispositions of businesses (2) | (41.8) |  |
Measurement period adjustments | 6.8 |  |
Finite-lived Intangible Assets [Roll Forward] |  |  |
Acquisitions of businesses | 99.4 | 497.4 |
Foreign currency translation | 2.5 | (3.2) |
Amortization | (21.8) | (18.8) |
Goodwill and Intangible Assets [Roll Forward] |  |  |
Beginning balance | 537.5 | 62.1 |
Write-off | (10.4) |  |
Ending balance | 654.7 | 537.5 | 62.1
Intangible Asset and Goodwill | Renewal Rights |  |  |
Finite-lived Intangible Assets [Roll Forward] |  |  |
Acquisitions of businesses | 82.5 |  |
MediaAlpha | Other Intangible Assets |  |  |
Goodwill [Roll Forward] |  |  |
Dispositions of businesses (2) | (23.5) |  |
Finite-lived Intangible Assets [Roll Forward] |  |  |
Write-off | (2.8) |  |
Other Operations |  |  |
Goodwill and Intangible Assets [Roll Forward] |  |  |
Goodwill, impairment loss | 7.6 |  |
Impairments | 0.4 |  |
NSM Holding Co LLC |  |  |
Goodwill [Roll Forward] |  |  |
Beginning balance | 354.3 |  |
Ending balance | 381.6 | 354.3 |
Finite-lived Intangible Assets [Roll Forward] |  |  |
Amortization | (19.4) | (8.3) | $ 0.0
Goodwill and Intangible Assets [Roll Forward] |  |  |
Impairments | 2.4 |  |
NSM Holding Co LLC | Renewal Rights |  |  |
Goodwill and Intangible Assets [Roll Forward] |  |  |
Impairments | 0.0 |  |
NSM Holding Co LLC | Goodwill |  |  |
Goodwill [Roll Forward] |  |  |
Foreign currency translation | 1.4 | $ (2.2) |
Fresh Insurance Services Group Limited |  |  |
Goodwill and Intangible Assets [Roll Forward] |  |  |
Impairments | 2.4 |  |
KBK Insurance Group, Inc. & KBK Premium Services, Inc. | Goodwill |  |  |
Goodwill [Roll Forward] |  |  |
Measurement period adjustments(5) | $ 5.9 |  |

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