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+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 28
-Subparagraph (b)
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-Section 45
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-Publisher FASB
-Name Accounting Standards Codification
-Topic 225
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-Section S99
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Reference 4: http://www.xbrl.org/2003/role/presentationRef
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-Number 210
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-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Section 04
-Paragraph 11
-Article 7

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Amount of current income tax expense (benefit) and deferred income tax expense (benefit) pertaining to continuing operations.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 9
-Subparagraph (a),(b)
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-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 1
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-URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e23780-122690

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-Publisher FASB
-Name Accounting Standards Codification
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-URI http://asc.fasb.org/extlink&oid=6515339

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Carrying value of a distribution

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No definition available.

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- Definition

The net unrealized gains (losses) from Symetra's fixed maturity portfolio.

+ References

No definition available.

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Total investments in (A) companies that are accounted for using the equity method and (B) warrants to acquire additional shares of an unconsolidated affiliate that are carried at fair value.

+ References

No definition available.

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- References

No definition available.

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Investments in Unconsolidated Affiliates (Investments in Symetra Table Rollforward) (Details) - USD ($) $ in Millions	3 Months Ended			6 Months Ended		10 Months Ended	12 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Mar. 31, 2015	Jun. 30, 2016	Jun. 30, 2015	Nov. 05, 2015	Dec. 31, 2015
Changes in carrying value of investment in Symetra
Equity in earnings	$ 0.0	$ 6.8		$ 0.0	$ 14.1
Income Tax Expense (Benefit)	$ (6.0)	(2.2)		$ (15.7)	2.4
Symetra \| Common Stock
Changes in carrying value of investment in Symetra
Carrying value at the beginning of the period		447.3	$ 411.4		411.4	$ 411.4	$ 411.4
Equity in earnings		6.1			13.3
Equity in net unrealized gains (losses) from Symetra's fixed maturity portfolio		(66.4)			(35.5)
Dividends received		(2.2)	(2.2)		(4.4)	$ (4.4)
Carrying value of a distribution		12.4			12.4
Carrying value at the end of the period		397.2	$ 447.3		$ 397.2
White Mountains \| Common Stock
Changes in carrying value of investment in Symetra
Equity in net unrealized gains (losses) from Symetra's fixed maturity portfolio		2.0
equity in earnings of unconsolidated affiliates \| Symetra \| Common Stock
Changes in carrying value of investment in Symetra
Income Tax Expense (Benefit)		0.4					0.8
Net unrealized gains (losses) of unconsolidated affiliates \| White Mountains \| Common Stock
Changes in carrying value of investment in Symetra
Income Tax Expense (Benefit)		0.0
Amortization of common share basis difference \| Symetra \| Common Stock
Changes in carrying value of investment in Symetra
Equity in earnings		0.7					1.4
impairment of net unrealized gains (losses) \| Net unrealized gains (losses) of unconsolidated affiliates \| Symetra \| Common Stock
Changes in carrying value of investment in Symetra
Equity in net unrealized gains (losses) from Symetra's fixed maturity portfolio		$ 2.8					$ 5.7