XML 177 R157.htm IDEA: XBRL DOCUMENT
v3.3.1.900

SCHEDULE I SUMMARY OF INVESTMENTS-OTHER THAN INVESTMENTS IN RELATED PARTIES (Details) - USD ($) $ in Millions | Dec. 31, 2015 | Dec. 31, 2014 | Dec. 31, 2013
--- | --- | --- | ---
Summary of investments other than investments in related parties |  |  |
Cost | $ 3,958.8 |  |
Carrying Value | 4,262.2 |  |
Fair Value | 4,262.2 |  |
Fair value investments | 4,050.9 | $ 3,343.6 | $ 3,889.0
Fixed maturity investments |  |  |
Summary of investments other than investments in related parties |  |  |
Cost | 2,639.1 |  |
Carrying Value | 2,639.7 |  |
Fair Value | 2,639.7 |  |
US Government and agency obligations |  |  |
Summary of investments other than investments in related parties |  |  |
Cost | 160.4 |  |
Carrying Value | 160.0 |  |
Fair Value | 160.0 |  |
Debt securities issued by corporations |  |  |
Summary of investments other than investments in related parties |  |  |
Cost | 1,001.0 |  |
Carrying Value | 1,000.0 |  |
Fair Value | 1,000.0 |  |
Municipal obligations |  |  |
Summary of investments other than investments in related parties |  |  |
Cost | 227.8 |  |
Carrying Value | 228.8 |  |
Fair Value | 228.8 |  |
Mortgage-backed and asset-backed securities |  |  |
Summary of investments other than investments in related parties |  |  |
Cost | 1,170.6 |  |
Carrying Value | 1,167.0 |  |
Fair Value | 1,167.0 |  |
Foreign government, agency and provincial obligations |  |  |
Summary of investments other than investments in related parties |  |  |
Cost | 1.0 |  |
Carrying Value | 1.2 |  |
Fair Value | 1.2 |  |
Redeemable preferred stocks |  |  |
Summary of investments other than investments in related parties |  |  |
Cost | 78.3 |  |
Carrying Value | 82.7 |  |
Fair Value | 82.7 |  |
Short-term investments |  |  |
Summary of investments other than investments in related parties |  |  |
Cost | 211.3 |  |
Carrying Value | 211.3 |  |
Fair Value | 211.3 |  |
Exchange Traded Funds [Member] |  |  |
Summary of investments other than investments in related parties |  |  |
Cost | 147.2 |  |
Carrying Value | 141.8 |  |
Fair Value | 141.8 |  |
Common equity securities |  |  |
Summary of investments other than investments in related parties |  |  |
Cost | 822.5 |  |
Carrying Value | 1,113.9 |  |
Fair Value | 1,113.9 |  |
Banks, trust and insurance companies |  |  |
Summary of investments other than investments in related parties |  |  |
Cost | 436.9 |  |
Carrying Value | 694.7 |  |
Fair Value | 694.7 |  |
Public utilities |  |  |
Summary of investments other than investments in related parties |  |  |
Cost | 0.0 |  |
Carrying Value | 0.0 |  |
Fair Value | 0.0 |  |
Industrial, miscellaneous and other |  |  |
Summary of investments other than investments in related parties |  |  |
Cost | 238.4 |  |
Carrying Value | 277.4 |  |
Fair Value | 277.4 |  |
Other long-term investments |  |  |
Summary of investments other than investments in related parties |  |  |
Cost | 285.9 |  |
Carrying Value | 297.3 |  |
Fair Value | 297.3 |  |
Fair value measured on a recurring basis |  |  |
Summary of investments other than investments in related parties |  |  |
Fair value investments | 4,262.2 | 3,720.4 |
Fair value measured on a recurring basis | Other long-term investments |  |  |
Summary of investments other than investments in related parties |  |  |
Fair value investments | 297.3 | 309.9 |
Level 3 | Other long-term investments |  |  |
Summary of investments other than investments in related parties |  |  |
Fair value investments | 297.3 | 304.2 | 189.2
Level 3 | Fair value measured on a recurring basis |  |  |
Summary of investments other than investments in related parties |  |  |
Fair value investments | 367.3 | 420.1 |
Level 3 | Fair value measured on a recurring basis | Other long-term investments |  |  |
Summary of investments other than investments in related parties |  |  |
Carrying value of investment accounted for using the equity method | 3.8 | 5.2 | $ 6.8
Fair value investments | 297.3 | 304.2 |
Affordable Housing Development Fund [Member] | Other long-term investments |  |  |
Summary of investments other than investments in related parties |  |  |
Fair value investments | $ 14.7 | $ 16.8 |

X
- Definition Fair value portion of investments accounted under the equity method. + References Reference 1: 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=35740979&loc=d3e32014-111567 + Details
Name: | us-gaap_EquityMethodInvestmentsFairValueDisclosure
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Fair value portion of investment securities, including, but not limited to, marketable securities, derivative financial instruments, and investments accounted for under the equity method. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Trading Securities -URI http://asc.fasb.org/extlink&oid=6526789 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 35 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=27723805&loc=d3e24584-111560 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 25 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=51813488&loc=d3e22054-111558 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Available-for-Sale Securities -URI http://asc.fasb.org/extlink&oid=6505594 Reference 5: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 03 -Paragraph 1 -Subparagraph a, f, g -Article 7 + Details
Name: | us-gaap_InvestmentsFairValueDisclosure
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

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 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=50485924&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 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=50485924&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 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=50485924&loc=d3e611379-123010 + Details
Name: | us-gaap_SummaryOfInvestmentsOtherThanInvestmentsInRelatedPartiesFairValue
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

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_SummaryOfInvestmentsOtherThanInvestmentsInRelatedPartiesReportableDataLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Details
Name: | us-gaap_SummaryOfInvestmentsOtherThanInvestmentsInRelatedPartiesByTypeAxis=us-gaap_FixedMaturitiesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_SummaryOfInvestmentsOtherThanInvestmentsInRelatedPartiesByTypeAxis=us-gaap_USTreasuryAndGovernmentMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_SummaryOfInvestmentsOtherThanInvestmentsInRelatedPartiesByTypeAxis=us-gaap_CorporateDebtSecuritiesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_SummaryOfInvestmentsOtherThanInvestmentsInRelatedPartiesByTypeAxis=us-gaap_MunicipalBondsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_SummaryOfInvestmentsOtherThanInvestmentsInRelatedPartiesByTypeAxis=us-gaap_AssetBackedSecuritiesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_SummaryOfInvestmentsOtherThanInvestmentsInRelatedPartiesByTypeAxis=us-gaap_ForeignGovernmentDebtSecuritiesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_SummaryOfInvestmentsOtherThanInvestmentsInRelatedPartiesByTypeAxis=us-gaap_PreferredStockMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_SummaryOfInvestmentsOtherThanInvestmentsInRelatedPartiesByTypeAxis=us-gaap_ShortTermInvestmentsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_SummaryOfInvestmentsOtherThanInvestmentsInRelatedPartiesByTypeAxis=us-gaap_ExchangeTradedFundsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_SummaryOfInvestmentsOtherThanInvestmentsInRelatedPartiesByTypeAxis=us-gaap_EquitySecuritiesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_SummaryOfInvestmentsOtherThanInvestmentsInRelatedPartiesByTypeAxis=us-gaap_BanksTrustAndInsuranceEquitiesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_SummaryOfInvestmentsOtherThanInvestmentsInRelatedPartiesByTypeAxis=us-gaap_PublicUtilityEquitiesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_SummaryOfInvestmentsOtherThanInvestmentsInRelatedPartiesByTypeAxis=us-gaap_IndustrialMiscellaneousAndAllOthersMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_SummaryOfInvestmentsOtherThanInvestmentsInRelatedPartiesByTypeAxis=us-gaap_OtherLongTermInvestmentsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FairValueByMeasurementFrequencyAxis=us-gaap_FairValueMeasurementsRecurringMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis=us-gaap_OtherLongTermInvestmentsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_FairValueByFairValueHierarchyLevelAxis=us-gaap_FairValueInputsLevel3Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | invest_InvestmentAxis=wtm_AffordableHousingDevelopmentFundMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |