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Investments in Unconsolidated Entities - White Mountain's Investments (Details)	Mar. 31, 2020	Dec. 31, 2019	May 31, 2019
Schedule of Equity Method Investments [Line Items]
Ownership interest (as a percent)	50.00%	50.00%
MediaAlpha
Schedule of Equity Method Investments [Line Items]
Ownership interest (as a percent)	48.30%	48.30%
durchblicker
Schedule of Equity Method Investments [Line Items]
Ownership interest (as a percent)	45.00%	45.00%
Elementum Holdings, L.P.
Schedule of Equity Method Investments [Line Items]
Ownership interest (as a percent)	30.00%	30.00%	30.00%
Compare.com
Schedule of Equity Method Investments [Line Items]
Ownership interest (as a percent)	18.40%	18.40%
JAM Partners L.P.
Schedule of Equity Method Investments [Line Items]
Ownership interest (as a percent)		11.10%
Minimum | Tuckerman Capital Funds
Schedule of Equity Method Investments [Line Items]
Ownership interest (as a percent)	16.10%	17.50%
Minimum | Enlightenment Capital Funds
Schedule of Equity Method Investments [Line Items]
Ownership interest (as a percent)	9.60%	10.00%
Minimum | Kudu Investments
Schedule of Equity Method Investments [Line Items]
Ownership interest (as a percent)	3.20%	3.20%
Maximum | Tuckerman Capital Funds
Schedule of Equity Method Investments [Line Items]
Ownership interest (as a percent)	61.30%	62.40%
Maximum | Enlightenment Capital Funds
Schedule of Equity Method Investments [Line Items]
Ownership interest (as a percent)	36.50%	38.40%
Maximum | Kudu Investments
Schedule of Equity Method Investments [Line Items]
Ownership interest (as a percent)	30.00%	30.00%

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

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 323
-SubTopic 10
-Section 50
-Paragraph 3
-Subparagraph (a)(1)
-URI http://asc.fasb.org/extlink&oid=114001798&loc=d3e33918-111571

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