XML 107 R147.htm IDEA: XBRL DOCUMENT
v2.4.0.8

Commitments and Contingencies (Legal Contingencies) (Details) (USD $) In Millions, unless otherwise specified | 12 Months Ended |  | 12 Months Ended
--- | --- | --- | ---
Dec. 31, 2013 | Dec. 31, 2012 | Dec. 31, 2011 | Jun. 30, 2007 Tribune Company Litigation | Dec. 31, 2011 Esurance
Legal Contingency [Abstract] |  |  |  |  |
Sales of unconsolidated affiliates, net of cash sold and held in escrow | $ 32.4 | $ 24.8 | $ 1,010.6 |  |
Gain (Loss) on Disposition of Business |  |  |  |  | 700.0
Period for which company has indemnified Allstate for breaches of representations and warranties (in months) |  | 18 months |  |  |
Period for which the entity has agreed not to solicit certain employees of transferred subsidiaries (in years) |  | 3 years |  |  |
Percentage of positive or negative development in the loss reserves of the Transferred Subsidiaries retained | 90.00% |  |  |  |
Proceeds in connection with Tribune leveraged buyout |  |  |  | $ 39 |

X
- Definition Gain (loss) from sale or disposal of an organization or integrated set of activities (for example, but not limited to, a partnership or corporation) engaged in providing a product or service in a commercial, industrial, or professional environment. + References No definition available. + Details
Name: | us-gaap_GainLossOnSaleOfBusiness
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

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

X
- Definition The cash inflow associated with the deconsolidation of a previously consolidated subsidiary or sale of an entity that is related to it but not strictly controlled. + References Reference 1: 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 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 12 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3179-108585 + Details
Name: | us-gaap_ProceedsFromDivestitureOfInterestInSubsidiariesAndAffiliates
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Percentage of favorable or unfavorable loss reserve development in the Transferred Subsidiaries retained by the entity. + References No definition available. + Details
Name: | wtm_PercentageOfFluctuationInLossReservesOfTransferredSubsidiariesRetained
Namespace Prefix: | wtm_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | instant

X
- Definition Represents the period from the transaction closing date for which the entity has agreed not to solicit certain employees of the transferred subsidiaries as per the covenants of sale agreement for the sale of subsidiaries. + References No definition available. + Details
Name: | wtm_PeriodForWhichEntityHasAgreedNotToSolicitCertainEmployeesOfTransferredSubsidiaries
Namespace Prefix: | wtm_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration

X
- Definition Represents the period from the transaction closing date for which the entity has provided indemnity to the counterparty of the agreement against the breaches of representations and warranties specified in the sale agreement for the sale of subsidiaries. + References No definition available. + Details
Name: | wtm_PeriodOfIndemnificationForBreachesOfRepresentationsAndWarranties
Namespace Prefix: | wtm_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration

X
- Definition Proceeds from common stock tendered in connection with a leveraged buyout. + References No definition available. + Details
Name: | wtm_ProceedsFromCommonStock
Namespace Prefix: | wtm_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant