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Goodwill and Other Intangible Assets (Goodwill and Intangible Assets) (Details) - USD ($) $ in Millions | 12 Months Ended |  |  |  |  |
--- | --- | --- | --- | --- | --- | ---
Dec. 31, 2016 | Aug. 04, 2016 | Dec. 31, 2015 | Dec. 31, 2014 | Mar. 14, 2014 | Feb. 19, 2014
Goodwill [Line Items] |  |  |  |  |  |
Intangible Assets, Gross (Excluding Goodwill) | $ 58.6 |  | $ 53.6 |  |  |
Amortization of Intangible Assets | 34.4 |  | 22.3 |  |  |
Intangible Assets, Net (Excluding Goodwill) | 24.2 |  | 31.3 | $ 38.7 |  |
Goodwill | 31.7 |  | 24.1 | $ 23.8 |  |
Intangible Assets, Gross (Including Goodwill) | 90.3 |  | 77.7 |  |  |
Goodwill and intangible assets | 55.9 |  | 55.4 |  |  |
MediaAlpha |  |  |  |  |  |
Goodwill [Line Items] |  |  |  |  |  |
Intangible Assets, Gross (Excluding Goodwill) | 42.4 |  | 38.5 |  |  |
Amortization of Intangible Assets | 24.1 |  | 14.1 |  |  |
Intangible Assets, Net (Excluding Goodwill) | 18.3 |  | 24.4 |  | $ 38.5 |
Goodwill | 18.3 |  | 18.3 |  | $ 18.3 |
WOBI [Member] |  |  |  |  |  |
Goodwill [Line Items] |  |  |  |  |  |
Intangible Assets, Gross (Excluding Goodwill) | 5.7 |  | 5.7 |  |  |
Amortization of Intangible Assets | 2.0 |  | 1.2 |  |  |
Intangible Assets, Net (Excluding Goodwill) | 3.7 |  | 4.5 |  |  |
Goodwill | 5.8 |  | 5.8 |  |  | $ 5.5
Buzzmove [Member] |  |  |  |  |  |
Goodwill [Line Items] |  |  |  |  |  |
Intangible Assets, Gross (Excluding Goodwill) | 1.1 |  | 0.0 |  |  |
Amortization of Intangible Assets | 0.1 |  | 0.0 |  |  |
Intangible Assets, Net (Excluding Goodwill) | 1.0 | $ 1.1 | 0.0 |  |  |
Goodwill | 7.6 | $ 7.6 | 0.0 |  |  |
Developed Technology Rights [Member] | MediaAlpha |  |  |  |  |  |
Goodwill [Line Items] |  |  |  |  |  |
Intangible Assets, Gross (Excluding Goodwill) | 32.4 |  | 32.0 |  |  |
Amortization of Intangible Assets | 17.9 |  | 11.2 |  |  |
Intangible Assets, Net (Excluding Goodwill) | $ 14.5 |  | 20.8 |  |  |
Acquired Finite-lived Intangible Assets, Weighted Average Useful Life | 5 years |  |  |  |  |
Developed Technology Rights [Member] | WOBI [Member] |  |  |  |  |  |
Goodwill [Line Items] |  |  |  |  |  |
Intangible Assets, Gross (Excluding Goodwill) | $ 3.6 |  | 3.6 |  |  |
Amortization of Intangible Assets | 1.2 |  | 0.7 |  |  |
Intangible Assets, Net (Excluding Goodwill) | $ 2.4 |  | 2.9 |  |  |
Acquired Finite-lived Intangible Assets, Weighted Average Useful Life | 7 years |  |  |  |  |
Developed Technology Rights [Member] | Buzzmove [Member] |  |  |  |  |  |
Goodwill [Line Items] |  |  |  |  |  |
Intangible Assets, Gross (Excluding Goodwill) | $ 0.5 |  | 0.0 |  |  |
Amortization of Intangible Assets | 0.0 |  | 0.0 |  |  |
Intangible Assets, Net (Excluding Goodwill) | $ 0.5 |  | 0.0 |  |  |
Acquired Finite-lived Intangible Assets, Weighted Average Useful Life | 5 years |  |  |  |  |
Customer Relationships [Member] | MediaAlpha |  |  |  |  |  |
Goodwill [Line Items] |  |  |  |  |  |
Intangible Assets, Gross (Excluding Goodwill) | $ 10.0 |  | 6.5 |  |  |
Amortization of Intangible Assets | 6.2 |  | 2.9 |  |  |
Intangible Assets, Net (Excluding Goodwill) | $ 3.8 |  | 3.6 |  |  |
Acquired Finite-lived Intangible Assets, Weighted Average Useful Life | 3 years |  |  |  |  |
Trademarks [Member] | WOBI [Member] |  |  |  |  |  |
Goodwill [Line Items] |  |  |  |  |  |
Intangible Assets, Gross (Excluding Goodwill) | $ 2.1 |  | 2.1 |  |  |
Amortization of Intangible Assets | 0.8 |  | 0.5 |  |  |
Intangible Assets, Net (Excluding Goodwill) | $ 1.3 |  | 1.6 |  |  |
Acquired Finite-lived Intangible Assets, Weighted Average Useful Life | 8 years |  |  |  |  |
Trademarks [Member] | Buzzmove [Member] |  |  |  |  |  |
Goodwill [Line Items] |  |  |  |  |  |
Intangible Assets, Gross (Excluding Goodwill) | $ 0.6 |  | 0.0 |  |  |
Amortization of Intangible Assets | 0.1 |  | 0.0 |  |  |
Intangible Assets, Net (Excluding Goodwill) | $ 0.5 |  | 0.0 |  |  |
Acquired Finite-lived Intangible Assets, Weighted Average Useful Life | 7 years |  |  |  |  |
Other Intangible Assets [Member] | OneBeacon |  |  |  |  |  |
Goodwill [Line Items] |  |  |  |  |  |
Intangible Assets, Gross (Excluding Goodwill) | $ 9.4 |  | 9.4 |  |  |
Amortization of Intangible Assets | 8.2 |  | 7.0 |  |  |
Intangible Assets, Net (Excluding Goodwill) | $ 1.2 |  | $ 2.4 |  |  |
Acquired Finite-lived Intangible Assets, Weighted Average Useful Life | 10 years |  |  |  |  |

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