XML 75 R55.htm IDEA: XBRL DOCUMENT
v3.3.1.900

Discontinued Operations (Tables) | 12 Months Ended
--- | ---
Dec. 31, 2015
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items] |
Summary of the fair value and carrying value of financial instruments | The following table summarizes the fair values and book values as of December 31, 2015 and 2014:
|  | December 31, 2015 |  | December 31, 2014
Millions |  | Fair Value |  | Carrying Value |  | Fair Value |  | Carrying Value
OBH Senior Notes |  | $ | 276.4 |  |  | $ | 274.8 |  |  | $ | 286.0 |  |  | $ | 274.7 |
Tranzact Bank Facility |  | 102.8 |  |  | 102.9 |  |  | 68.7 |  |  | 67.4 |
MediaAlpha Bank Facility |  | 15.0 |  |  | 14.7 |  |  | — |  |  | — |
Schedule illustrating the valuation adjustments between par and fair value [Table Text Block] | Below is a table illustrating the valuation adjustments taken to arrive at the estimated fair value of the OneBeacon Surplus Notes as of December 23, 2014:
|  | Type of Surplus Note |  |
Millions |  | Seller Priority |  | Pari Passu |  | Total
Par Value |  | $ | 57.9 |  |  | $ | 43.1 |  |  | $ | 101.0 |
Fair value adjustments to reflect: |  |  |  |  |  |
Current market rates on public debt and contract-based repayments(1) |  | 1.6 |  |  | (8.4 | ) |  | (6.8 | )
Regulatory approval (2) |  | (4.6 | ) |  | (8.0 | ) |  | (12.6 | )
Liquidity adjustment (3) |  | (11.0 | ) |  | (5.7 | ) |  | (16.7 | )
Total adjustments |  | (14.0 | ) |  | (22.1 | ) |  | (36.1 | )
Fair value |  | $ | 43.9 |  |  | $ | 21.0 |  |  | $ | 64.9 |
(1) | Represents the value of the OneBeacon Surplus Notes, at current market yields on publicly traded debt, and assuming issuer is allowed to make principal and interest payments when its financial capacity is available, as measured by statutory capital in excess of a 250% RBC score.
(2) | Represents anticipated delay in securing regulatory approvals of interest and principal payments to reflect graduated changes in Issuer’s statutory surplus. The monetary impact of the anticipated delay is measured based on credit spreads of public securities with roughly equivalent percentages of discounted payments missed.
(3) | Represents impact of liquidity spread to account for OneBeacon’s sole ownership of the surplus notes, lack of a trading market and ongoing regulatory approval risk.
Schedule of discontinued operations balance sheet, income statement, and cash flows | The following summarizes the assets and liabilities associated with the business classified as held for sale, which all relate to Sirius Group with the exception of the building held by OneBeacon at December 31, 2014:
|  | December 31,
Millions |  | 2015 |  | 2014
Assets held for sale |  |  |  |
Fixed maturity investments, at fair value |  | $ | 2,374.0 |  |  | $ | 2,362.3 |
Short term |  | 352.0 |  |  | 494.9 |
Common Equities |  | 174.4 |  |  | 189.9 |
Other |  | 72.2 |  |  | 95.6 |
Total Investments |  | 2,972.6 |  |  | 3,142.7 |
Cash |  | 143.9 |  |  | 111.5 |
Reinsurance recoverable on unpaid losses |  | 283.1 |  |  | 322.2 |
Reinsurance recoverable on paid losses |  | 10.2 |  |  | 11.4 |
Insurance premiums receivable |  | 323.6 |  |  | 306.6 |
Deferred acquisition costs |  | 74.6 |  |  | 69.9 |
Deferred tax asset |  | 303.1 |  |  | 341.5 |
Ceded unearned insurance and reinsurance premiums |  | 87.7 |  |  | 76.2 |
Accounts receivable on unsettled investment sales |  | 29.0 |  |  | 18.7 |
Intangible assets |  | 10.2 |  |  | 15.2 |
Other assets |  | 169.0 |  |  | 156.6 |
Other assets - OneBeacon building |  | — |  |  | 58.1 |
Total assets held for sale |  | $ | 4,407.0 |  |  | $ | 4,630.6 |
Liabilities held for sale |  |  |  |
Loss and loss adjustment expense reserves |  | $ | 1,644.4 |  |  | $ | 1,809.8 |
Unearned insurance premiums |  | 342.2 |  |  | 338.6 |
Debt |  | 403.5 |  |  | 403.5 |
Deferred tax liability |  | 263.6 |  |  | 282.8 |
Accrued incentive compensation |  | 63.2 |  |  | 76.5 |
Ceded reinsurance payable |  | 67.1 |  |  | 71.5 |
Funds held under reinsurance treaties |  | 52.9 |  |  | 57.9 |
Accounts payable on unsettled investment purchases |  | — |  |  | 2.1 |
Other liabilities |  | 47.1 |  |  | 62.6 |
Total liabilities held for sale |  | 2,884.0 |  |  | 3,105.3 |
Net assets held for sale |  | $ | 1,523.0 |  |  | $ | 1,525.3 |
Net Income (Loss) from Discontinued Operations The following summarizes the results of operations, including related income taxes associated with the business classified as discontinued operations. The results of Sirius Group through the closing date of the transaction inures to White Mountains.
|  | Year Ended December 31, 2015
Millions |  | Sirius Group |  | Other Disc Ops |  | Total
Revenues |  |  |  |  |  |  |
Earned insurance premiums |  | $ | 847.0 |  |  | $ | — |  |  | $ | 847.0 |
Net investment income |  | 40.7 |  |  | — |  |  | 40.7 |
Net realized and unrealized investment gains |  | 15.1 |  |  | — |  |  | 15.1 |
Other revenue |  | (20.6 | ) |  | (.7 | ) |  | (21.3 | )
Total revenues |  | 882.2 |  |  | (.7 | ) |  | 881.5 |
Expenses |  |  |  |  |  |
Loss and loss adjustment expenses |  | 422.7 |  |  | — |  |  | 422.7 |
Insurance and reinsurance acquisition expenses |  | 189.8 |  |  | — |  |  | 189.8 |
Other underwriting expenses |  | 107.9 |  |  | — |  |  | 107.9 |
Interest expense on debt |  | 26.6 |  |  | — |  |  | 26.6 |
General and administrative expenses |  | 27.0 |  |  | — |  |  | 27.0 |
Total expenses |  | 774.0 |  |  | — |  |  | 774.0 |
Pre-tax income (loss) |  | 108.2 |  |  | (.7 | ) |  | 107.5 |
Income tax expense |  | (27.1 | ) |  | .2 |  |  | (26.9 | )
Net income (loss) from discontinued operations |  | 81.1 |  |  | (.5 | ) |  | 80.6 |
Net gain from sales of discontinued operations - OneBeacon |  | — |  |  | .3 |  |  | .3 |
Net gain from sales of discontinued operations - Esurance |  | — |  |  | 17.9 |  |  | 17.9 |
Total income from discontinued operations |  | 81.1 |  |  | 17.7 |  |  | 98.8 |
Change in foreign currency translation and other from discontinued operations |  | (65.0 | ) |  | — |  |  | (65.0 | )
Comprehensive income from discontinued operations |  | $ | 16.1 |  |  | $ | 17.7 |  |  | $ | 33.8 |
|  | Year Ended December 31, 2014
Millions |  | Sirius Group |  | Other Disc Ops |  | Total
Revenues |  |  |  |  |  |  |
Earned insurance premiums |  | $ | 873.9 |  |  | $ | .1 |  |  | $ | 874.0 |
Net investment income |  | 40.9 |  |  | — |  |  | 40.9 |
Net realized and unrealized investment gains |  | 205.4 |  |  | — |  |  | 205.4 |
Other revenue |  | (62.4 | ) |  | — |  |  | (62.4 | )
Total revenues |  | 1,057.8 |  |  | .1 |  |  | 1,057.9 |
Expenses |  |  |  |  |  |  |
Loss and loss adjustment expenses |  | 345.3 |  |  | (.7 | ) |  | 344.6 |
Insurance and reinsurance acquisition expenses |  | 193.6 |  |  | .1 |  |  | 193.7 |
Other underwriting expenses |  | 129.7 |  |  | 3.5 |  |  | 133.2 |
Interest expense on debt |  | 26.3 |  |  | — |  |  | 26.3 |
General and administrative expenses |  | 30.5 |  |  | — |  |  | 30.5 |
Total expenses |  | 725.4 |  |  | 2.9 |  |  | 728.3 |
Pre-tax income (loss) |  | 332.4 |  |  | (2.8 | ) |  | 329.6 |
Income tax (expense) benefit |  | (70.4 | ) |  | 1.0 |  |  | (69.4 | )
Net income (loss) from discontinued operations |  | 262.0 |  |  | (1.8 | ) |  | 260.2 |
Net gain from sales of discontinued operations - FFIC |  | — |  |  | 14.0 |  |  | 14.0 |
Net losses from sales of discontinued operations - OneBeacon |  | — |  |  | (18.8 | ) |  | (18.8 | )
Net gain from sales of discontinued operations - Esurance |  | — |  |  | 3.2 |  |  | 3.2 |
Total income from discontinued operations |  | 262.0 |  |  | (3.4 | ) |  | 258.6 |
Change in foreign currency translation and other from discontinued operations |  | (169.5 | ) |  | — |  |  | (169.5 | )
Comprehensive income (loss) from discontinued operations |  | $ | 92.5 |  |  | $ | (3.4 | ) |  | $ | 89.1 |
|  | Year Ended December 31, 2013
Millions |  | Sirius Group |  | Other Disc Ops |  | Total
Revenues |  |  |  |  |  |  |
Earned insurance premiums |  | $ | 866.4 |  |  | $ | .8 |  |  | $ | 867.2 |
Net investment income |  | 46.7 |  |  | — |  |  | 46.7 |
Net realized and unrealized investment gains |  | 27.8 |  |  | — |  |  | 27.8 |
Other revenue |  | 16.8 |  |  | 10.8 |  |  | 27.6 |
Total revenues |  | 957.7 |  |  | 11.6 |  |  | 969.3 |
Expenses |  |  |  |  |  |  |
Loss and loss adjustment expenses |  | 418.4 |  |  | 78.9 |  |  | 497.3 |
Insurance and reinsurance acquisition expenses |  | 166.5 |  |  | — |  |  | 166.5 |
Other underwriting expenses |  | 126.1 |  |  | (.2 | ) |  | 125.9 |
Interest expense on debt |  | 26.3 |  |  | — |  |  | 26.3 |
General and administrative expenses |  | 32.2 |  |  | — |  |  | 32.2 |
Total expenses |  | 769.5 |  |  | 78.7 |  |  | 848.2 |
Pre-tax income (loss) |  | 188.2 |  |  | (67.1 | ) |  | 121.1 |
Income tax (expense) benefit |  | (46.2 | ) |  | 25.0 |  |  | (21.2 | )
Net income (loss) from discontinued operations |  | 142.0 |  |  | (42.1 | ) |  | 99.9 |
Net gain from sales of discontinued operations |  | — |  |  | 46.6 |  |  | 46.6 |
Total income from discontinued operations |  | 142.0 |  |  | 4.5 |  |  | 146.5 |
Change in foreign currency translation and other from discontinued operations |  | 6.1 |  |  | — |  |  | 6.1 |
Comprehensive income from discontinued operations |  | $ | 148.1 |  |  | $ | 4.5 |  |  | $ | 152.6 |
Net Change in Cash from Discontinued Operations The following summarizes the net change in cash associated with the businesses classified as discontinued operations:
|  | Year ended
|  | December 31,
Millions |  | 2015 |  | 2014 |  | 2013
Net cash provided from (used for) operations |  | $ | 14.7 |  |  | $ | 60.0 |  |  | $ | (61.5 | )
Net cash provided from investing activities |  | 31.3 |  |  | 35.8 |  |  | 148.7 |
Net cash used for financing activities |  | (9.1 | ) |  | (63.2 | ) |  | (87.5 | )
Effect of exchange rate changes on cash |  | (4.5 | ) |  | (14.3 | ) |  | (.2 | )
Net change in cash during the period |  | 32.4 |  |  | 18.3 |  |  | (.5 | )
Cash balances at beginning of period |  | 111.5 |  |  | 93.2 |  |  | 93.7 |
Cash balances at end of period |  | $ | 143.9 |  |  | $ | 111.5 |  |  | $ | 93.2 |
Discontinued operations, computation of earnings per share | The following table outlines the computation of earnings per share for discontinued operations for the years ended December 31, 2015, 2014 and 2013:
|  | Year Ended December 31,
|  | 2015 |  | 2014 |  | 2013
Basic and diluted earnings per share numerators (in millions): |  |  |  |  |  |  |  |
Net income attributable to White Mountains’s common shareholders |  | $ | 98.8 |  |  | $ | 258.6 |  |  | $ | 146.5 |
Allocation of income for participating unvested restricted common shares (1) |  | (1.1 | ) |  | (3.3 | ) |  | (2.2 | )
Net income attributable to White Mountains’s common shareholders, net of restricted common share amounts (2) |  | $ | 97.7 |  |  | $ | 255.3 |  |  | $ | 144.3 |
Basic earnings per share denominators (in thousands): |  |  |  |  |  |  |  |
Total average common shares outstanding during the period |  | 5,879.2 |  |  | 6,104.9 |  |  | 6,200.4 |
Average unvested restricted common shares (3) |  | (68.0 | ) |  | (78.9 | ) |  | (91.4 | )
Basic earnings per share denominator |  | 5,811.2 |  |  | 6,026.0 |  |  | 6,109.0 |
Diluted earnings per share denominator (in thousands): |  |  |  |  |  |  |  |
Total average common shares outstanding during the period |  | 5,879.2 |  |  | 6,104.9 |  |  | 6,200.4 |
Average unvested restricted common shares (3) |  | (68.0 | ) |  | (78.9 | ) |  | (91.4 | )
Average outstanding dilutive options to acquire common shares (4) |  | — |  |  | — |  |  | — |
Diluted earnings per share denominator |  | 5,811.2 |  |  | 6,026.0 |  |  | 6,109.0 |
Basic and diluted earnings per share (in dollars): |  | $ | 16.80 |  |  | $ | 42.36 |  |  | $ | 23.63 |
(1) | Restricted shares issued by White Mountains contain dividend participation features, and therefore, are considered participating securities.
(2) | Net income (loss) attributable to White Mountains’s common shareholders, net of restricted share amounts, is equal to undistributed earnings for the years ended December 31, 2015, 2014 and 2013.
(3) | Restricted common shares outstanding vest either in equal annual installments or upon a stated date (see Note 13 - “Employee Share-Based Incentive Compensation Plans”).
(4) | The diluted earnings (loss) per share denominator for the years ended December 31, 2015, 2014 and 2013 does not include the impact of 125,000 common shares issuable upon exercise of the non-qualified options outstanding as they are anti-dilutive to the calculation.
Sirius Group |
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items] |
Summary of the fair value and carrying value of financial instruments | The following table summarizes the fair value and carrying value of the Sirius Group financials instruments, the SIG Senior Notes and the SIG Preference Shares, as of December 31, 2015 and 2014:
|  | December 31, 2015 |  | December 31, 2014
Millions |  | Fair Value |  | Carrying Value |  | Fair Value |  | Carrying Value
SIG Senior Notes |  | $ | 410.0 |  |  | $ | 399.8 |  |  | $ | 437.8 |  |  | $ | 399.7 |
SIG Preference Shares |  | 255.0 |  |  | 250.0 |  |  | 260.0 |  |  | 250.0 |
Interest Rate Cap | Sirius Group |
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items] |
Fair Value of Assets and Liabilities Measured on Recurring and Non-recurring Basis Table | The following table summarizes the change in the fair value of the Interest Rate Cap for the year ended December 31, 2015:
|  | December 31,
Millions |  | 2015 |  | 2014
Beginning of period |  | $ | 4.1 |  |  | $ | 11.1 |
Net realized and unrealized losses |  | (2.2 | ) |  | (7.0 | )
End of period |  | $ | 1.9 |  |  | $ | 4.1 |
Schedule of collateral | The following table summarizes the Interest Rate Cap collateral balances held by White Mountains and ratings by counterparty:
|  | December 31, 2015
Millions |  | Collateral Balances Held |  | Standard & Poor’s Rating(1)
Barclays Bank Plc |  | $ | 1.3 |  |  | A-
Nordea Bank Finland Plc |  | .6 |  |  | AA-
Total |  | $ | 1.9 |  |  |
(1) | Standard & Poor’s ratings as detailed above are: “A” (Strong, which is the sixth highest of twenty-one creditworthiness ratings) and “AA-” (Very Strong, which is the fourth highest of twenty-one creditworthiness ratings).

X
- Definition Tabular disclosure of the fair value measurement of assets using significant unobservable inputs (Level 3), a reconciliation of the beginning and ending balances, separately presenting changes during the period attributable to the following: (1) total gains or losses for the period (realized and unrealized), segregating those gains or losses included in earnings (or changes in net assets) and gains or losses recognized in other comprehensive income (loss), and a description of where those gains or losses included in earnings (or changes in net assets) are reported in the statement of income (or activities); (2) purchases, sales, issues, and settlements (each type disclosed separately); and (3) transfers in and transfers out of Level 3 (for example, transfers due to changes in the observability of significant inputs), by class of asset. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 820 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=36462937&loc=d3e19207-110258 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 820 -SubTopic 10 -Section 50 -Paragraph 3 -URI http://asc.fasb.org/extlink&oid=36462937&loc=d3e19279-110258 + Details
Name: | us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationTextBlock
Namespace Prefix: | us-gaap_
Data Type: | nonnum:textBlockItemType
Balance Type: | na
Period Type: | duration

X
- Definition Tabular disclosure of the fair value of financial instruments, including financial assets and financial liabilities, and the measurements of those instruments, assets, and liabilities. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 825 -SubTopic 10 -Section 50 -Paragraph 12 -URI http://asc.fasb.org/extlink&oid=49121117&loc=d3e13476-108611 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 820 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=36462937&loc=d3e19207-110258 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 825 -SubTopic 10 -Section 50 -Paragraph 11 -URI http://asc.fasb.org/extlink&oid=49121117&loc=d3e13467-108611 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 825 -SubTopic 10 -Section 45 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=6447952&loc=d3e13220-108610 Reference 5: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 825 -SubTopic 10 -Section 50 -Paragraph 30 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=6957238&loc=d3e14172-108612 Reference 6: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 825 -SubTopic 10 -Section 50 -Paragraph 10 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=49121117&loc=d3e13433-108611 + Details
Name: | us-gaap_FairValueByBalanceSheetGroupingTextBlock
Namespace Prefix: | us-gaap_
Data Type: | nonnum:textBlockItemType
Balance Type: | na
Period Type: | duration

X
- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. + References No definition available. + Details
Name: | us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Tabular disclosure of information related to a disposal group. Includes, but is not limited to, a discontinued operation, disposal classified as held-for-sale or disposed of by means other than sale or disposal of an individually significant component. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 205 -SubTopic 20 -Section 45 -Paragraph 11 -URI http://asc.fasb.org/extlink&oid=51716988&loc=SL51721533-107759 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 205 -SubTopic 20 -Section 50 -Paragraph 4B -URI http://asc.fasb.org/extlink&oid=51717284&loc=SL51721665-107760 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 205 -SubTopic 20 -Section 50 -Paragraph 3 -URI http://asc.fasb.org/extlink&oid=51717284&loc=d3e1474-107760 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 205 -SubTopic 20 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=51717284&loc=d3e1361-107760 Reference 5: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 205 -SubTopic 20 -Section 50 -Paragraph 7 -URI http://asc.fasb.org/extlink&oid=51717284&loc=SL51721683-107760 Reference 6: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 360 -SubTopic 10 -Section 50 -Paragraph 3A -URI http://asc.fasb.org/extlink&oid=51719941&loc=SL51724579-110230 Reference 7: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 205 -SubTopic 20 -Section 50 -Paragraph 5C -URI http://asc.fasb.org/extlink&oid=51717284&loc=SL51721675-107760 Reference 8: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 205 -SubTopic 20 -Section 50 -Paragraph 4A -URI http://asc.fasb.org/extlink&oid=51717284&loc=SL51721663-107760 Reference 9: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 360 -SubTopic 10 -Section 50 -Paragraph 3 -URI http://asc.fasb.org/extlink&oid=51719941&loc=d3e2941-110230 Reference 10: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 205 -SubTopic 20 -Section 50 -Paragraph 5B -URI http://asc.fasb.org/extlink&oid=51717284&loc=SL51721673-107760 Reference 11: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 205 -SubTopic 20 -Section 50 -Paragraph 3A -URI http://asc.fasb.org/extlink&oid=51717284&loc=SL51721659-107760 Reference 12: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 205 -SubTopic 20 -Section 50 -Paragraph 5A -URI http://asc.fasb.org/extlink&oid=51717284&loc=SL51721671-107760 Reference 13: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 205 -SubTopic 20 -Section 50 -Paragraph 5D -URI http://asc.fasb.org/extlink&oid=51717284&loc=SL51721677-107760 + Details
Name: | us-gaap_ScheduleOfDisposalGroupsIncludingDiscontinuedOperationsIncomeStatementBalanceSheetAndAdditionalDisclosuresTextBlock
Namespace Prefix: | us-gaap_
Data Type: | nonnum:textBlockItemType
Balance Type: | na
Period Type: | duration

X
- Definition Tabular disclosure of the numerators and the denominators of the basic and diluted per-share (or per-unit) computations for income from discontinued operations, including the effect that has been given to preferred dividends. + References No definition available. + Details
Name: | wtm_ScheduleOfDiscontinuedOperationsCalculationOfNumeratorAndDenominatorInEarningsPerShareTableTextBlock
Namespace Prefix: | wtm_
Data Type: | nonnum:textBlockItemType
Balance Type: | na
Period Type: | duration

X
- Definition Schedule illustrating the valuation adjustments between par and fair value [Table Text Block] + References No definition available. + Details
Name: | wtm_ScheduleillustratingthevaluationadjustmentsbetweenparandfairvalueTableTextBlock
Namespace Prefix: | wtm_
Data Type: | nonnum:textBlockItemType
Balance Type: | na
Period Type: | duration

X
- Definition Schedule of collateral [Table Text Block] + References No definition available. + Details
Name: | wtm_ScheduleofcollateralTableTextBlock
Namespace Prefix: | wtm_
Data Type: | nonnum:textBlockItemType
Balance Type: | na
Period Type: | duration

X
- Details
Name: | us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis=wtm_SiriusGroupMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_DerivativeInstrumentRiskAxis=us-gaap_InterestRateCapMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |