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Goodwill and Other Intangible Assets (Summary of Goodwill and Intangible Assets) (Details) - USD ($) $ in Millions | 12 Months Ended |
--- | --- | ---
Dec. 31, 2019 | Dec. 31, 2018 | Dec. 31, 2017
Goodwill [Line Items] |  |  |
Goodwill, fair value | $ 402.3 | $ 379.9 |
Goodwill, impairment loss | 7.6 |  |
Goodwill | 394.7 | 379.9 |
Other intangible assets, fair value | 694.4 | 591.1 |
Other intangible assets, accumulated amortization | 29.3 | 53.6 |
Other intangible assets, net | 251.4 |  |
Goodwill and Intangible Asset Impairment | 10.4 |  |
Goodwill and other intangible assets | 654.7 | 537.5 |
NSM Holding Co LLC |  |  |
Goodwill [Line Items] |  |  |
Goodwill, fair value | 381.6 | 354.3 |
Goodwill | 381.6 | 354.3 |
Other intangible assets, fair value | 271.7 | 140.2 |
Other intangible assets, accumulated amortization | 27.9 | 8.3 |
Impairments | 2.4 |  |
Other intangible assets, net | 241.4 | 131.9 |
Kudu |  |  |
Goodwill [Line Items] |  |  |
Goodwill, fair value | 7.6 | 0.0 |
Goodwill | 7.6 | 0.0 |
MediaAlpha |  |  |
Goodwill [Line Items] |  |  |
Goodwill, fair value | 0.0 | 18.3 |
Goodwill | 0.0 | 18.3 |
Other intangible assets, fair value | 0.0 | 69.9 |
Other intangible assets, accumulated amortization | 0.0 | 44.8 |
Impairments | 0.0 |  |
Other intangible assets, net | 0.0 | 25.1 |
Other |  |  |
Goodwill [Line Items] |  |  |
Goodwill, fair value | 13.1 | 7.3 |
Goodwill, impairment loss | 7.6 |  |
Goodwill | 5.5 | 7.3 |
Other intangible assets, fair value | 18.2 | 1.1 |
Other intangible assets, accumulated amortization | 1.2 | 0.5 |
Impairments | 0.4 |  |
Other intangible assets, net | $ 16.6 | 0.6 |
Customer Relationships | NSM Holding Co LLC |  |  |
Goodwill [Line Items] |  |  |
Acquired other intangible assets, weighted average useful life | 9 years |  |
Other intangible assets, fair value | $ 121.7 | 85.3 |
Other intangible assets, accumulated amortization | 19.8 | 6.0 |
Impairments | 1.4 |  |
Other intangible assets, net | $ 100.5 | 79.3 |
Customer Relationships | MediaAlpha |  |  |
Goodwill [Line Items] |  |  |
Acquired other intangible assets, weighted average useful life | 9 years |  |
Other intangible assets, fair value | $ 0.0 | 26.8 |
Other intangible assets, accumulated amortization | 0.0 | 4.9 |
Impairments | 0.0 |  |
Other intangible assets, net | $ 0.0 | 21.9 |
Customer Relationships | Other |  |  |
Goodwill [Line Items] |  |  |
Acquired other intangible assets, weighted average useful life | 11 years |  |
Other intangible assets, fair value | $ 7.2 | 0.0 |
Other intangible assets, accumulated amortization | 0.4 | 0.0 |
Other intangible assets, net | $ 6.8 | 0.0 |
Trade Names | NSM Holding Co LLC |  |  |
Goodwill [Line Items] |  |  |
Acquired other intangible assets, weighted average useful life | 19 years |  |
Other intangible assets, fair value | $ 61.9 | 51.2 |
Other intangible assets, accumulated amortization | 5.3 | 1.8 |
Impairments | 0.4 |  |
Other intangible assets, net | $ 56.2 | 49.4 |
Trade Names | Kudu |  |  |
Goodwill [Line Items] |  |  |
Acquired other intangible assets, weighted average useful life | 7 years |  |
Other intangible assets, fair value | $ 2.2 | 0.0 |
Other intangible assets, accumulated amortization | 0.2 | 0.0 |
Impairments | 0.0 |  |
Other intangible assets, net | $ 2.0 | 0.0 |
Trade Names | Other |  |  |
Goodwill [Line Items] |  |  |
Acquired other intangible assets, weighted average useful life | 10 years |  |
Other intangible assets, fair value | $ 1.7 | 0.6 |
Other intangible assets, accumulated amortization | 0.5 | 0.2 |
Impairments | 0.2 |  |
Other intangible assets, net | $ 1.0 | 0.4 |
Information Technology | NSM Holding Co LLC |  |  |
Goodwill [Line Items] |  |  |
Acquired other intangible assets, weighted average useful life | 5 years |  |
Other intangible assets, fair value | $ 3.9 | 3.7 |
Other intangible assets, accumulated amortization | 1.4 | 0.5 |
Impairments | 0.6 |  |
Other intangible assets, net | $ 1.9 | 3.2 |
Information Technology | MediaAlpha |  |  |
Goodwill [Line Items] |  |  |
Acquired other intangible assets, weighted average useful life | 5 years |  |
Other intangible assets, fair value | $ 0.0 | 33.3 |
Other intangible assets, accumulated amortization | 0.0 | 30.9 |
Impairments | 0.0 |  |
Other intangible assets, net | $ 0.0 | 2.4 |
Information Technology | Other |  |  |
Goodwill [Line Items] |  |  |
Acquired other intangible assets, weighted average useful life | 5 years |  |
Other intangible assets, fair value | $ 0.5 | 0.5 |
Other intangible assets, accumulated amortization | 0.3 | 0.3 |
Impairments | 0.2 |  |
Other intangible assets, net |  | 0.2 |
Insurance licenses | Other |  |  |
Goodwill [Line Items] |  |  |
Other intangible assets, fair value | 8.6 | 0.0 |
Other intangible assets, accumulated amortization | 0.0 | 0.0 |
Other intangible assets, net | $ 8.6 | 0.0 |
Renewal Rights | NSM Holding Co LLC |  |  |
Goodwill [Line Items] |  |  |
Acquired other intangible assets, weighted average useful life | 12 years |  |
Other intangible assets, fair value | $ 82.5 |  |
Other intangible assets, accumulated amortization | 0.7 |  |
Impairments | 0.0 |  |
Other intangible assets, net | $ 81.8 |  |
Other | NSM Holding Co LLC |  |  |
Goodwill [Line Items] |  |  |
Acquired other intangible assets, weighted average useful life | 3 years |  |
Other intangible assets, fair value | $ 1.7 |  |
Other intangible assets, accumulated amortization | 0.7 |  |
Impairments | 0.0 |  |
Other intangible assets, net | $ 1.0 |  |
Other | MediaAlpha |  |  |
Goodwill [Line Items] |  |  |
Acquired other intangible assets, weighted average useful life | 3 years |  |
Other intangible assets, fair value | $ 0.0 | 9.8 |
Other intangible assets, accumulated amortization | 0.0 | 9.0 |
Impairments | 0.0 |  |
Other intangible assets, net | $ 0.0 | 0.8 |
Other | Other |  |  |
Goodwill [Line Items] |  |  |
Acquired other intangible assets, weighted average useful life | 5 years |  |
Other intangible assets, fair value | $ 0.2 | 0.0 |
Other intangible assets, accumulated amortization | 0.0 | 0.0 |
Other intangible assets, net | 0.2 | 0.0 |
Other Intangible Assets |  |  |
Goodwill [Line Items] |  |  |
Other intangible assets, fair value | 292.1 | 211.2 |
Other intangible assets, accumulated amortization | 29.3 | 53.6 |
Impairments | 2.8 |  |
Other intangible assets, net | 260.0 | 157.6 |
Non-controlling Interests |  |  |
Goodwill [Line Items] |  |  |
Goodwill and other intangible assets | (23.4) | (40.6) |
Parent |  |  |
Goodwill [Line Items] |  |  |
Goodwill and other intangible assets | 631.3 | 496.9 |
Goodwill |  |  |
Goodwill [Line Items] |  |  |
Goodwill | 394.7 | 379.9 | $ 25.9
Goodwill, foreign currency translation gain | 1.8 | (2.5) |
Goodwill | NSM Holding Co LLC |  |  |
Goodwill [Line Items] |  |  |
Goodwill, foreign currency translation gain | 1.4 | (2.2) |
Goodwill | Other |  |  |
Goodwill [Line Items] |  |  |
Goodwill, foreign currency translation gain | 0.0 | (0.3) |
Other Intangible Assets | NSM Holding Co LLC |  |  |
Goodwill [Line Items] |  |  |
Goodwill, foreign currency translation gain | $ 0.7 | $ (0.7) |

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