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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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-Publisher FASB
-Name Accounting Standards Codification
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-Section S99
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Reference 4: http://www.xbrl.org/2003/role/presentationRef
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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	9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Jun. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Changes in carrying value of investment in Symetra
Equity in earnings	$ 0.0	$ 3.9		$ 0.0	$ 18.0
Income Tax Expense (Benefit)	$ (6.7)	(1.6)		$ (22.4)	0.8
Symetra \| Common Stock
Changes in carrying value of investment in Symetra
Carrying value at the beginning of the period		397.2	$ 411.4		411.4
Equity in earnings		4.2			17.5
Equity in net unrealized gains (losses) from Symetra's fixed maturity portfolio		3.7			(31.8)
Dividends received		(12.5)			(16.9)
Carrying value of a distribution		0.0			12.4
Carrying value at the end of the period		392.6	$ 397.2		392.6
White Mountains \| Common Stock
Changes in carrying value of investment in Symetra
Equity in net unrealized gains (losses) from Symetra's fixed maturity portfolio		5.7
equity in earnings of unconsolidated affiliates \| Symetra \| Common Stock
Changes in carrying value of investment in Symetra
Income Tax Expense (Benefit)		0.3			1.1
Net unrealized gains (losses) of unconsolidated affiliates \| White Mountains \| Common Stock
Changes in carrying value of investment in Symetra
Income Tax Expense (Benefit)		0.2
Amortization of common share basis difference \| Symetra \| Common Stock
Changes in carrying value of investment in Symetra
Equity in earnings		0.7			2.1
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		$ 2.9			$ 8.6