XML 65 R100.htm IDEA: XBRL DOCUMENT
v2.4.0.6

Investments in Unconsolidated Affiliates (Details 2) (Symetra, USD $) In Millions, except Share data, unless otherwise specified | 12 Months Ended |  | 1 Months Ended | 3 Months Ended
--- | --- | --- | --- | ---
Dec. 31, 2011 technic representative Y | Dec. 31, 2011 Minimum | Dec. 31, 2011 Maximum | Jan. 31, 2010 Initial public offering | Mar. 31, 2010 Initial public offering
Investments in unconsolidated affiliates |  |  |  |  |
Investments in unconsolidated affiliates (in shares) | 17,400,000 |  |  |  |
Additional common shares (in shares) | 9,500,000 |  |  |  |
Initial public offering issue price (in dollars per share) |  |  |  | $ 12.00 |
Sale of Symetra common shares by Symetra (in shares) |  |  |  | 25,300,000 |
Sale of Symetra common shares by existing shareholders (in shares) |  |  |  | 9,700,000 |
Ownership interest before initial public offering (as a percent) |  |  |  |  | 24.00%
Ownership interest after initial public offering (as a percent) |  |  |  |  | 20.00%
Decrease in carrying value of Symetra from dilution |  |  |  | $ 16.0 |
Ownership interest (as a percent) | 15.00% |  |  |  |
Fair value of investment | 261.0 |  |  |  |
Estimated fair value of investment per share | $ 15 | $ 16 | $ 30 |  |
Number of valuation techniques | 3 |  |  |  |
Number of representatives | 2 |  |  |  |
After-tax equity in losses of unconsolidated affiliates | 45.9 |  |  |  |
Equity in net unrealized gains (losses) | $ 136.6 |  |  |  |
Risk free interest rate (as a percent) | 0.31% |  |  |  |
Volatility rate (as a percent) | 36.00% |  |  |  |
Expected life (in years) | 2.58 |  |  |  |
Strike price (in dollars per share) | $ 11.49 |  |  |  |
Share price (in dollars per share) | $ 9.07 |  |  |  |

X
- Definition The percentage of ownership of common stock or equity participation in the investee accounted for under the equity method of accounting. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 159 -Paragraph 18 -Subparagraph f -LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009.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 AICPA -Name Accounting Principles Board Opinion (APB) -Number 18 -Paragraph 20 -Subparagraph a (1) -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 Accounting Standards Codification -Topic 323 -SubTopic 10 -Section 50 -Paragraph 3 -Subparagraph (a)(1) -URI http://asc.fasb.org/extlink&oid=6382943&loc=d3e33918-111571 + Details
Name: | us-gaap_EquityMethodInvestmentOwnershipPercentage
Namespace Prefix: | us-gaap_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | instant

X
- Definition This element represents the portion of the balance sheet assertion valued at fair value by the entity whether such amount is presented as a separate caption or as a parenthetical disclosure. Additionally, this element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. The element may be used in both the balance sheet and disclosure in the same submission. This item represents investments accounted for under the equity method of accounting as of the balance sheet date. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher AICPA -Name Accounting Principles Board Opinion (APB) -Number 18 -Paragraph 6 -Subparagraph b -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 -Topic 323 -SubTopic 10 -Section 25 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=6903542&loc=d3e32014-111567 + Details
Name: | us-gaap_EquityMethodInvestmentsFairValueDisclosure
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Balance held at close of period in number of shares. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 946 -SubTopic 320 -Section S99 -Paragraph 6 -Subparagraph (SX 210.12-14.Column B) -URI http://asc.fasb.org/extlink&oid=6955306&loc=d3e611322-123010 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 14 -Paragraph Column B -Article 12 + Details
Name: | us-gaap_InvestmentsInAndAdvancesToAffiliatesBalanceShares
Namespace Prefix: | us-gaap_
Data Type: | xbrli:sharesItemType
Balance Type: | na
Period Type: | instant

X
- Definition The number of shares issued or sold by the subsidiary or equity method investee per stock transaction. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Staff Accounting Bulletin (SAB) -Number Topic 5 -Section H + Details
Name: | us-gaap_SaleOfStockNumberOfSharesIssuedInTransaction
Namespace Prefix: | us-gaap_
Data Type: | xbrli:sharesItemType
Balance Type: | na
Period Type: | duration

X
- Definition Percentage of subsidiary's or equity investee's stock owned by parent company after stock transaction. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Staff Accounting Bulletin (SAB) -Number Topic 5 -Section H + Details
Name: | us-gaap_SaleOfStockPercentageOfOwnershipAfterTransaction
Namespace Prefix: | us-gaap_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition Percentage of subsidiary's or equity investee's stock owned by parent company before stock transaction. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Staff Accounting Bulletin (SAB) -Number Topic 5 -Section H + Details
Name: | us-gaap_SaleOfStockPercentageOfOwnershipBeforeTransaction
Namespace Prefix: | us-gaap_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition The dollar amount received by subsidiary or equity investee for each share of common stock issued or sold in the stock transaction. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Staff Accounting Bulletin (SAB) -Number Topic 5 -Section H + Details
Name: | us-gaap_SaleOfStockPricePerShare
Namespace Prefix: | us-gaap_
Data Type: | num:perShareItemType
Balance Type: | na
Period Type: | instant

X
- Details
Name: | us-gaap_SubsidiaryOrEquityMethodInvesteeLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition The time period during which a warrant is expected to be outstanding. + References No definition available. + Details
Name: | wtm_ClassOfWarrantOrRightFairValueAssumptionsExpectedTerm
Namespace Prefix: | wtm_
Data Type: | xbrli:decimalItemType
Balance Type: | na
Period Type: | duration

X
- Definition Volatility assumption used in valuing warrants. + References No definition available. + Details
Name: | wtm_ClassOfWarrantOrRightFairValueAssumptionsExpectedVolatilityRate
Namespace Prefix: | wtm_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition The price per share that is used in valuing warrants. + References No definition available. + Details
Name: | wtm_ClassOfWarrantOrRightFairValueAssumptionsPerSharePrice
Namespace Prefix: | wtm_
Data Type: | num:perShareItemType
Balance Type: | na
Period Type: | instant

X
- Definition The strike price per share that is used in valuing warrants. + References No definition available. + Details
Name: | wtm_ClassOfWarrantOrRightFairValueAssumptionsPerStrikePrice
Namespace Prefix: | wtm_
Data Type: | num:perShareItemType
Balance Type: | na
Period Type: | instant

X
- Definition The risk-free interest rate assumption that is used in valuing warrants. + References No definition available. + Details
Name: | wtm_ClassOfWarrantOrRightFairValueAssumptionsRiskFreeInterestRate
Namespace Prefix: | wtm_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition Decrease in the carrying value of Symetra resulting from the dilution caused by the issuance of new Symetra shares at a price below its adjusted book value per share. + References No definition available. + Details
Name: | wtm_DecreaseInCarryingValueOfSymetraFromDilution
Namespace Prefix: | wtm_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Represents fair value per share of investments accounted for under the equity method of accounting as of the balance sheet date. + References No definition available. + Details
Name: | wtm_EquityMethodInvestmentsFairValuePerShare
Namespace Prefix: | wtm_
Data Type: | num:perShareItemType
Balance Type: | na
Period Type: | instant

X
- Definition Represents the number of techniques used for valuation of equity method investments. + References No definition available. + Details
Name: | wtm_EquityMethodInvestmentsNumberOfValuationTechniques
Namespace Prefix: | wtm_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | duration

X
- Definition Represents the entity's after-tax loss from the impairment of Symetra common shares recorded in equity in change in net unrealized investment gains (losses). + References No definition available. + Details
Name: | wtm_ImpairmentOfSymetraCommonSharesChangeInNetUnrealizedGainsLosses
Namespace Prefix: | wtm_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Represents the entity's after-tax loss from the impairment of Symetra common shares recorded in equity in losses. + References No definition available. + Details
Name: | wtm_ImpairmentOfSymetraCommonSharesEquityInEarningsAfterTax
Namespace Prefix: | wtm_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Represents additional shares of an unconsolidated affiliate to be obtained on conversion of warrants. + References No definition available. + Details
Name: | wtm_InvestmentsInUnconsolidatedAffiliatesOnConversionOfWarrants
Namespace Prefix: | wtm_
Data Type: | xbrli:sharesItemType
Balance Type: | na
Period Type: | instant

X
- Definition Represents the number of representatives under Board of Directors. + References No definition available. + Details
Name: | wtm_NumberOfRepresentativesUnderBoardOfDirectors
Namespace Prefix: | wtm_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | duration

X
- Definition The number of shares sold by existing shareholders of a subsidiary or equity method investee excluding shares sold by the entity. + References No definition available. + Details
Name: | wtm_SaleOfStockNumberOfSharesSoldInTransactionByExistingShareholders
Namespace Prefix: | wtm_
Data Type: | xbrli:sharesItemType
Balance Type: | na
Period Type: | duration