XML 25 R112.htm IDEA: XBRL DOCUMENT
v2.4.0.6

SCHEDULE I SUMMARY OF INVESTMENTS-OTHER THAN INVESTMENTS IN RELATED PARTIES (Details) (USD $) In Millions, unless otherwise specified | Dec. 31, 2011
--- | ---
Summary of investments other than investments in related parties |
Cost | $ 8,179.5
Carrying Value | 8,379.8
Fair Value | 8,379.8
AutoOne |
Summary of investments other than investments in related parties |
Investments reclassified to assets held for sale | 111.8
Fixed maturity investments. |
Summary of investments other than investments in related parties |
Cost | 6,228.2
Carrying Value | 6,333.7
Fair Value | 6,333.7
U.S. Government and agency obligations |
Summary of investments other than investments in related parties |
Cost | 299.4
Carrying Value | 305.0
Fair Value | 305.0
Debt securities issued by corporations |
Summary of investments other than investments in related parties |
Cost | 2,072.1
Carrying Value | 2,135.1
Fair Value | 2,135.1
Mortgage-backed and asset-backed securities |
Summary of investments other than investments in related parties |
Cost | 3,190.5
Carrying Value | 3,222.9
Fair Value | 3,222.9
Municipal obligations |
Summary of investments other than investments in related parties |
Cost | 2.7
Carrying Value | 2.7
Fair Value | 2.7
Foreign government, agency and provincial obligations |
Summary of investments other than investments in related parties |
Cost | 581.2
Carrying Value | 589.2
Fair Value | 589.2
Non-cumulative perpetual preference shares |
Summary of investments other than investments in related parties |
Cost | 82.3
Carrying Value | 78.8
Fair Value | 78.8
Short-term investments |
Summary of investments other than investments in related parties |
Cost | 846.0
Carrying Value | 846.0
Fair Value | 846.0
Common equity securities |
Summary of investments other than investments in related parties |
Cost | 691.7
Carrying Value | 755.0
Fair Value | 755.0
Banks, trust and insurance companies |
Summary of investments other than investments in related parties |
Cost | 205.3
Carrying Value | 219.2
Fair Value | 219.2
Public utilities |
Summary of investments other than investments in related parties |
Cost | 39.4
Carrying Value | 42.0
Fair Value | 42.0
Industrial, miscellaneous and other |
Summary of investments other than investments in related parties |
Cost | 447.0
Carrying Value | 493.8
Fair Value | 493.8
Convertible fixed maturities |
Summary of investments other than investments in related parties |
Cost | 139.2
Carrying Value | 143.8
Fair Value | 143.8
Other long-term investments |
Summary of investments other than investments in related parties |
Cost | 274.4
Carrying Value | 301.3
Fair Value | $ 301.3

X
- Definition This element represents the carrying (reported) amount of the entity's investments as of the balance sheet date. This amount may represent the individual investment's or group of similar investments' original cost, fair value, or such other amount at which the investment is shown in the entity's balance sheet. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 15 -Article 12 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 946 -SubTopic 320 -Section S99 -Paragraph 7 -Subparagraph (SX 210.12-15) -URI http://asc.fasb.org/extlink&oid=6955306&loc=d3e611379-123010 + Details
Name: | us-gaap_SummaryOfInvestmentsOtherThanInvestmentsInRelatedPartiesCarryingAmount
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition This item represents the original cost of the entity's investments including investments in equity securities and, as to fixed maturities, original cost reduced by repayments and adjusted for amortization of premiums or accrual of discounts. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 15 -Article 12 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 946 -SubTopic 320 -Section S99 -Paragraph 7 -Subparagraph (SX 210.12-15) -URI http://asc.fasb.org/extlink&oid=6955306&loc=d3e611379-123010 + Details
Name: | us-gaap_SummaryOfInvestmentsOtherThanInvestmentsInRelatedPartiesCost
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition This item represents the reported amount of the entity's investments measured at fair value. Fair value is the price that would be received to sell an investment in an orderly transaction between market participants at the balance sheet [measurement] date. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 15 -Article 12 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 946 -SubTopic 320 -Section S99 -Paragraph 7 -Subparagraph (SX 210.12-15) -URI http://asc.fasb.org/extlink&oid=6955306&loc=d3e611379-123010 + Details
Name: | us-gaap_SummaryOfInvestmentsOtherThanInvestmentsInRelatedPartiesFairValue
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

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

X
- Definition Represents the fair value of trading debt securities re-classified to assets held for sale. + References No definition available. + Details
Name: | wtm_TradingSecuritiesDebtReclassifiedToAssetsHeldForSale
Namespace Prefix: | wtm_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant