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Goodwill and Other Intangible Assets - Goodwill and Intangible Assets (Details) - USD ($) $ in Millions	Sep. 30, 2017	Jun. 30, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Dec. 31, 2015
Acquired Finite-Lived Intangible Assets [Line Items]
Goodwill	$ 25.9	$ 25.9	$ 25.9	$ 25.9	$ 18.3	$ 18.6
Goodwill and other intangible assets	37.8	40.3	45.2	47.7	41.6	45.5
MediaAlpha
Acquired Finite-Lived Intangible Assets [Line Items]
Goodwill	18.3		18.3
Buzzmove
Acquired Finite-Lived Intangible Assets [Line Items]
Goodwill	7.6		7.6
Other Intangible Assets
Acquired Finite-Lived Intangible Assets [Line Items]
Intangible Assets, Net (Excluding Goodwill)	11.9	$ 14.4	19.3	$ 21.8	$ 23.3	$ 26.9
Other Intangible Assets | MediaAlpha
Acquired Finite-Lived Intangible Assets [Line Items]
Intangible Assets, Net (Excluding Goodwill)	11.0		18.3
Other Intangible Assets | Buzzmove
Acquired Finite-Lived Intangible Assets [Line Items]
Intangible Assets, Net (Excluding Goodwill)	0.9		1.0
Discontinued Operations, Held-for-sale
Acquired Finite-Lived Intangible Assets [Line Items]
Goodwill and other intangible assets	0.0		1.2
Non-controlling interest
Acquired Finite-Lived Intangible Assets [Line Items]
Goodwill and other intangible assets	(13.7)		(17.1)
Total
Acquired Finite-Lived Intangible Assets [Line Items]
Goodwill and other intangible assets	$ 24.1		$ 29.3

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Amount after accumulated impairment loss of an asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 20
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Sum of the carrying amounts of all intangible assets, excluding goodwill, as of the balance sheet date, net of accumulated amortization and impairment charges.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
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Carrying amount of finite-lived intangible assets, indefinite-lived intangible assets and goodwill. Goodwill is an asset representing the future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized. Intangible assets are assets, not including financial assets, lacking physical substance.

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