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Derivatives (Pre-Tax Operating Results of WM Life Re) (Details) (USD $) In Millions, unless otherwise specified | 3 Months Ended
--- | ---
Mar. 31, 2013 | Mar. 31, 2012
Pre-tax operating results of WM Life Re |  |
Total revenues | $ 627.4 | $ 629.6
General and administrative expenses | (43.8) | (45.5)
Pre-tax income from continuing operations | 151.8 | 140.8
White Mountains Life Re |  |
Pre-tax operating results of WM Life Re |  |
Fees, included in other revenues | 6.8 | 8.0
Change in fair value of variable annuity liability, included in other revenues | 184.3 | 211.2
Realized and unrealized (losses) gains | (181.8) | (206.5)
Foreign exchange, included in other revenues | (14.6) | (23.0)
Other investment income and gains (losses) | (4.0) | (2.1)
Total revenues | (9.3) | (12.4)
Change in fair value of variable annuity death benefit liabilities, included in other general and administrative expenses | 5.6 | 8.8
Death benefit claims paid, included in general and administrative expenses | (1.1) | (1.8)
General and administrative expenses | (1.7) | (1.3)
Pre-tax income from continuing operations | $ (6.5) | $ (6.7)

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