XML 33 R55.htm IDEA: XBRL DOCUMENT
v2.4.0.6

Summary of Significant Accounting Policies (Foreign Currency Exchange) (Details) In Millions, unless otherwise specified | Dec. 31, 2012 USD ($) | Dec. 31, 2011 USD ($) | Dec. 31, 2012 SEK | Dec. 31, 2011 SEK | Dec. 31, 2010 SEK | Dec. 31, 2012 GBP GBP (£) | Dec. 31, 2011 GBP GBP (£) | Dec. 31, 2010 GBP GBP (£) | Dec. 31, 2012 Canada, Dollars CAD | Dec. 31, 2011 Canada, Dollars CAD | Dec. 31, 2010 Canada, Dollars CAD
--- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | ---
Significant Transactions |  |  |  |  |  |  |  |  |  |  |
Foreign currency exchange rate |  |  | 6.4973 | 6.8645 | 6.7030 | 0.6154 | 0.6434 | 0.6420 | 0.9955 | 1.0193 | 0.9981
Net unrealized foreign currency translation gains | $ 85.7 | $ 46.1 |  |  |  |  |  |  |  |  |

X
- Definition Accumulated adjustment, net of tax, that results from the process of translating subsidiary financial statements and foreign equity investments into the reporting currency from the functional currency of the reporting entity, net of reclassification of realized foreign currency translation gains or losses. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 52 -Paragraph 12, 13 -LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009.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 Statement of Financial Accounting Standard (FAS) -Number 130 -Paragraph 17, 18, 19, 22, 23, 24, 25, 26 -LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009.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 220 -SubTopic 10 -Section 45 -Paragraph 11 -URI http://asc.fasb.org/extlink&oid=20435746&loc=d3e637-108580 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher AICPA -Name Accounting Principles Board Opinion (APB) -Number 12 -Paragraph 10 -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 5: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 220 -SubTopic 10 -Section 45 -Paragraph 10A -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=20435746&loc=SL7669646-108580 Reference 6: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 52 -Paragraph 31 -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 7: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 220 -SubTopic 10 -Section 45 -Paragraph 14 -URI http://asc.fasb.org/extlink&oid=20435746&loc=d3e681-108580 Reference 8: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 133 -Paragraph 45 -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 9: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 830 -SubTopic 30 -Section 45 -Paragraph 12 -URI http://asc.fasb.org/extlink&oid=6915805&loc=d3e32022-110900 Reference 10: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 220 -SubTopic 10 -Section 45 -Paragraph 14A -URI http://asc.fasb.org/extlink&oid=20435746&loc=SL7669686-108580 Reference 11: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 830 -SubTopic 30 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6450520&loc=d3e32583-110901 + Details
Name: | us-gaap_AccumulatedOtherComprehensiveIncomeLossForeignCurrencyTranslationAdjustmentNetOfTax
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Foreign exchange rate used to translate amounts denominated in functional currency to reporting currency. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 830 -SubTopic 30 -Section S99 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6897108&loc=SL6897125-166521 + Details
Name: | us-gaap_ForeignCurrencyExchangeRateTranslation1
Namespace Prefix: | us-gaap_
Data Type: | xbrli:pureItemType
Balance Type: | na
Period Type: | instant

X
- Details
Name: | wtm_SignificantTransactionsLineItems
Namespace Prefix: | wtm_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration