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Non-controlling Interest (Details) - USD ($) $ in Millions	Sep. 30, 2018	Dec. 31, 2017
Noncontrolling Interest [Line Items]
Total non-controlling interests	$ (144.4)	$ (131.7)
Total Non-Controlling Excluding Reciprocals
Noncontrolling Interest [Line Items]
Total non-controlling interests	$ 45.7	$ 31.5
HG Global
Noncontrolling Interest [Line Items]
Noncontrolling equity percentage	3.10%	3.10%
Total non-controlling interests	$ 14.8	$ 15.9
NSM Holding Co LLC
Noncontrolling Interest [Line Items]
Noncontrolling equity percentage	5.00%	0.00%
Total non-controlling interests	$ 14.1	$ 0.0
MediaAlpha
Noncontrolling Interest [Line Items]
Noncontrolling equity percentage	37.80%	35.70%
Total non-controlling interests	$ 15.3	$ 13.1
Buzzmove
Noncontrolling Interest [Line Items]
Noncontrolling equity percentage	22.90%	22.90%
Total non-controlling interests	$ 1.5	$ 2.5
Build America Mutual
Noncontrolling Interest [Line Items]
Noncontrolling equity percentage	100.00%	100.00%
Total non-controlling interests	$ (190.1)	$ (163.2)

X

- Definition

Total of all stockholders' equity (deficit) items, net of receivables from officers, directors, owners, and affiliates of the entity which is directly or indirectly attributable to that ownership interest in subsidiary equity which is not attributable to the parent (that is, noncontrolling interest, previously referred to as minority interest).

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03(a)(24))
-URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910

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-Name Accounting Standards Codification
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