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SCHEDULE II CONDENSED FINANCIAL INFORMATION OF THE REGISTRANT (Details 3) (USD $) In Millions, unless otherwise specified | 3 Months Ended | 12 Months Ended |
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Dec. 31, 2011 | Sep. 30, 2011 | Jun. 30, 2011 | Mar. 31, 2011 | Dec. 31, 2010 | Sep. 30, 2010 | Jun. 30, 2010 | Mar. 31, 2010 | Dec. 31, 2011 | Dec. 31, 2010 | Dec. 31, 2009 | Dec. 31, 2008
CONDENSED FINANCIAL INFORMATION OF THE REGISTRANT |  |  |  |  |  |  |  |  |  |  |  |
Net income attributable to White Mountains' common shareholders | $ 800.2 | $ (15.8) | $ 11.7 | $ (28.2) | $ 72.9 | $ 50.7 | $ 2.5 | $ (39.6) | $ 767.9 | $ 86.5 | $ 470.0 |
Charges (credits) to reconcile net income to net cash (used for) provided from operations: |  |  |  |  |  |  |  |  |  |  |  |
Net realized and unrealized investment (gains) losses |  |  |  |  |  |  |  |  | (122.8) | (82.6) | (361.7) |
Net federal income tax (payments) receipts |  |  |  |  |  |  |  |  | 12.5 | (47.0) | (17.5) |
Net change in other assets and liabilities, net |  |  |  |  |  |  |  |  | (96.5) | (238.6) | 27.5 |
Net cash (used for) provided from operations |  |  |  |  |  |  |  |  | (114.5) | 56.0 | (46.7) |
Cash flows from investing activities: |  |  |  |  |  |  |  |  |  |  |  |
Net decrease in short-term investments |  |  |  |  |  |  |  |  | 174.5 | 475.6 | 218.4 |
Net change in unsettled investment purchases and sales |  |  |  |  |  |  |  |  | 47.0 | 1.6 | 52.1 |
Net cash provided from investing activities |  |  |  |  |  |  |  |  | 799.6 | 485.3 | 365.1 |
Cash flows from financing activities: |  |  |  |  |  |  |  |  |  |  |  |
Repayment of debt |  |  |  |  |  |  |  |  |  | (14.0) | (242.8) |
Proceeds from issuances of common shares |  |  |  |  |  |  |  |  | 0.9 | 0.7 | 0.9 |
Repurchases and retirement of common shares |  |  |  |  |  |  |  |  | (253.0) | (225.6) | (0.4) |
Dividends paid on common shares |  |  |  |  |  |  |  |  | (8.0) | (8.8) | (8.9) |
Net cash (used for) provided from financing activities |  |  |  |  |  |  |  |  | (460.2) | (550.2) | (360.2) |
Net increase (decrease) in cash during year |  |  |  |  |  |  |  |  | 223.4 | (0.8) | (35.0) |
Cash balance at beginning of year | 251.9 |  |  |  | 103.6 |  |  |  | 251.9 | 103.6 | 119.9 | 158.7
Cash balance at end of year | 251.9 |  |  |  | 103.6 |  |  |  | 251.9 | 103.6 | 119.9 | 158.7
White Mountains Insurance Group Ltd. |  |  |  |  |  |  |  |  |  |  |  |
CONDENSED FINANCIAL INFORMATION OF THE REGISTRANT |  |  |  |  |  |  |  |  |  |  |  |
Net income attributable to White Mountains' common shareholders |  |  |  |  |  |  |  |  | 767.9 | 86.5 | 470.0 |
Charges (credits) to reconcile net income to net cash (used for) provided from operations: |  |  |  |  |  |  |  |  |  |  |  |
Net realized and unrealized investment (gains) losses |  |  |  |  |  |  |  |  | (3.1) | 0.1 | 1.7 |
Undistributed current (earnings) losses from subsidiaries |  |  |  |  |  |  |  |  | (806.7) | (128.2) | (511.9) |
Dividends received from subsidiaries |  |  |  |  |  |  |  |  |  |  | 8.4 |
Net change in other assets and liabilities, net |  |  |  |  |  |  |  |  | 13.7 | 27.9 | 18.6 |
Net cash (used for) provided from operations |  |  |  |  |  |  |  |  | (28.2) | (13.7) | (13.2) |
Cash flows from investing activities: |  |  |  |  |  |  |  |  |  |  |  |
Net decrease in short-term investments |  |  |  |  |  |  |  |  | 267.3 | 166.5 | 20.8 |
Purchases of investment securities |  |  |  |  |  |  |  |  | (237.3) | (5.8) | (28.4) |
Sales and maturities of investment securities |  |  |  |  |  |  |  |  | 59.0 |  |  |
Issuance of debt (to) from subsidiaries |  |  |  |  |  |  |  |  |  | 86.8 |  |
Repayment of debt (to) from subsidiaries |  |  |  |  |  |  |  |  | 192.5 |  | 200.0 |
Distributions from subsidiaries |  |  |  |  |  |  |  |  | 7.2 |  | 29.0 |
Net cash provided from investing activities |  |  |  |  |  |  |  |  | 288.7 | 247.5 | 221.4 |
Cash flows from financing activities: |  |  |  |  |  |  |  |  |  |  |  |
Repayment of debt |  |  |  |  |  |  |  |  |  |  | (200.0) |
Proceeds from issuances of common shares |  |  |  |  |  |  |  |  | 0.9 | 0.7 | 0.9 |
Repurchases and retirement of common shares |  |  |  |  |  |  |  |  | (253.0) | (225.6) | (0.4) |
Dividends paid on common shares |  |  |  |  |  |  |  |  | (8.0) | (8.8) | (8.9) |
Net cash (used for) provided from financing activities |  |  |  |  |  |  |  |  | (260.1) | (233.7) | (208.4) |
Net increase (decrease) in cash during year |  |  |  |  |  |  |  |  | 0.4 | 0.1 | (0.2) |
Cash balance at beginning of year | 0.7 |  |  |  | 0.3 |  |  |  | 0.7 | 0.3 | 0.2 | 0.4
Cash balance at end of year | $ 0.7 |  |  |  | $ 0.3 |  |  |  | $ 0.7 | $ 0.3 | $ 0.2 | $ 0.4

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- Definition The cash outflow from the distribution of an entity's earnings in the form of dividends to common shareholders. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 15 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=6943989&loc=d3e3291-108585 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 95 -Paragraph 18 -LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy. Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 95 -Paragraph 20 -Subparagraph a -LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy. Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Financing Activities -URI http://asc.fasb.org/extlink&oid=6513228 + Details
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- Definition The cash outflow associated with the purchase of all investments (debt, security, other) during the period. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 95 -Paragraph 15, 17 -LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy. Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Investing Activities -URI http://asc.fasb.org/extlink&oid=6516133 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 13 -URI http://asc.fasb.org/extlink&oid=6943989&loc=d3e3213-108585 + Details
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- Definition The cash inflow from the additional capital contribution to the entity. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 14 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=6943989&loc=d3e3255-108585 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 95 -Paragraph 18 -LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy. Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 95 -Paragraph 19 -Subparagraph a -LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy. Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Financing Activities -URI http://asc.fasb.org/extlink&oid=6513228 + Details
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- Definition The cash inflow associated with the sale, maturities, repayments and calls of securities classified as trading securities and held for investment purposes. Excludes proceeds from trading securities purchased and held principally for the purpose of selling them in the near term (thus held for only a short period of time). + References No definition available. + Details
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- Definition The cash outflow during the period from the repayment of aggregate short-term and long-term debt. Excludes payment of capital lease obligations. + References No definition available. + Details
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- Definition The net change during the reporting period in accounts receivable on unsettled investment sales and accounts payable on unsettled investment purchases. + References No definition available. + Details
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