Value of capital units or capital shares. This element is relevant to issuers of face-amount certificates and registered investment companies.

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 946
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-Paragraph 1
-Subparagraph (SX 210.6-04.16(a))
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- Definition

Amount after tax of gain (loss) not previously recognized resulting from the disposal of a discontinued operation.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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- Definition

This element represents the aggregate cost of investments accounted for under the equity method of accounting.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.12)
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- Definition

The percentage of ownership of common stock or equity participation in the investee accounted for under the equity method of accounting.

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-Publisher FASB
-Name Accounting Standards Codification
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-SubTopic 10
-Section 50
-Paragraph 3
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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

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- Definition

The cash outflow associated with the acquisition of a controlling interest in another entity or an entity that is related to it but not strictly controlled (for example, an unconsolidated subsidiary, affiliate, joint venture or equity method investment).

+ References

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-Name Accounting Standards Codification
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-SubTopic 10
-Section 45
-Paragraph 13
-Subparagraph (b)
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The cash outflow associated with the acquisition of a business, net of the cash acquired from the purchase.

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The cash inflow associated with the deconsolidation of a previously consolidated subsidiary or sale of an entity that is related to it but not strictly controlled.

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Capital Units, Purchased

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No definition available.

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Significant Transactions (Details) - USD ($) $ in Millions						3 Months Ended			12 Months Ended
Significant Transactions (Details) - USD ($) $ in Millions	Jan. 24, 2018	Oct. 05, 2017	Sep. 28, 2017	Oct. 05, 2016	Jul. 21, 2016	Mar. 31, 2018	Dec. 31, 2017	Mar. 31, 2017	Dec. 31, 2016	Feb. 05, 2018
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Gain from sale of other discontinued operations, net of tax						$ 0.1	$ 0.1	$ (1.0)
Healthplans.com
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Payments to acquire businesses and interest in affiliates		$ 28.0
MediaAlpha
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Ownership interest (as a percent)						62.30%	64.40%
OneBeacon
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Sales of unconsolidated affiliates and consolidated subsidiaries, net of cash sold			$ 1,300.0
Gain from sale of other discontinued operations, net of tax			$ 554.6
Tranzact
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Sales of unconsolidated affiliates and consolidated subsidiaries, net of cash sold				$ 1.2	$ 221.3
Gain from sale of other discontinued operations, net of tax									$ 51.9
DavidShield & PassportCard
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Equity method investment, aggregate cost	$ 42.0
Payments to acquire business, net	$ 28.0
Ownership interest (as a percent)	50.00%
Kudu Investment Management, LLC
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Equity method investment, aggregate cost						$ 1.8				$ 127.5
Ownership interest (as a percent)						50.00%	0.00%
Capital Unit, Class A \| MediaAlpha
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Capital units, purchased		131,579
Capital units, value		$ 12.5