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Significant Transactions (Tables)

9 Months Ended

Sep. 30, 2016

Organization, Consolidation and Presentation of Financial Statements [Abstract]

Reconciliation to the increase in book value

A reconciliation of the gain reported in discontinued operations to the impact to White Mountains's book value is as follows:

Gain from sale of Tranzact reported in discontinued operations		$	51.9
Add back reclassification from continuing operations for the release of      a tax valuation allowance		30.2
Increase to White Mountains book value from sale of Tranzact		$	82.1

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[Table Text Block] for Reconciliation of net gain reported in discontinued operations to the increase in book value

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