XML 107 R140.htm IDEA: XBRL DOCUMENT
v2.4.1.9

Segment Information (Details) (USD $) In Millions, unless otherwise specified | 3 Months Ended | 12 Months Ended
--- | --- | ---
Dec. 31, 2014 | Sep. 30, 2014 | Jun. 30, 2014 | Mar. 31, 2014 | Dec. 31, 2013 | Sep. 30, 2013 | Jun. 30, 2013 | Mar. 31, 2013 | Dec. 31, 2014 | Dec. 31, 2013 | Dec. 31, 2012
Segment reporting information |  |  |  |  |  |  |  |  |  |  |
Percentage of par value of policy reinsured | 15.00%wtm_PercentageOfParValueOfPolicyReinsured |  |  |  |  |  |  |  | 15.00%wtm_PercentageOfParValueOfPolicyReinsured |  |
Earned insurance and reinsurance premiums |  |  |  |  |  |  |  |  | $ 2,058.9 us-gaap_PremiumsEarnedNet | $ 1,987.3 us-gaap_PremiumsEarnedNet | $ 2,063.6 us-gaap_PremiumsEarnedNet
Net investment income |  |  |  |  |  |  |  |  | 105.0 us-gaap_NetInvestmentIncome | 110.9 us-gaap_NetInvestmentIncome | 153.6 us-gaap_NetInvestmentIncome
Net investment income (loss) - surplus note interest |  |  |  |  |  |  |  |  | 0 wtm_NetInvestmentIncomeSurplusNotes | 0 wtm_NetInvestmentIncomeSurplusNotes | 0 wtm_NetInvestmentIncomeSurplusNotes
Net realized and unrealized investment gains |  |  |  |  |  |  |  |  | 283.9 us-gaap_GainLossOnInvestments | 161.7 us-gaap_GainLossOnInvestments | 118.2 us-gaap_GainLossOnInvestments
Other revenue |  |  |  |  |  |  |  |  | 62.4 us-gaap_OtherIncome | 57.5 us-gaap_OtherIncome | 100.3 us-gaap_OtherIncome
Total revenues | 689.7 us-gaap_Revenues | 589.4 us-gaap_Revenues | 652.8 us-gaap_Revenues | 578.3 us-gaap_Revenues | 626.6 us-gaap_Revenues | 574.1 us-gaap_Revenues | 489.3 us-gaap_Revenues | 627.4 us-gaap_Revenues | 2,510.2 us-gaap_Revenues | 2,317.4 us-gaap_Revenues | 2,435.7 us-gaap_Revenues
Loss and loss adjustment expenses |  |  |  |  |  |  |  |  | 1,169.3 us-gaap_PolicyholderBenefitsAndClaimsIncurredNet | 1,040.5 us-gaap_PolicyholderBenefitsAndClaimsIncurredNet | 1,193.9 us-gaap_PolicyholderBenefitsAndClaimsIncurredNet
Insurance and reinsurance acquisition expenses |  |  |  |  |  |  |  |  | 399.8 wtm_InsuranceAndReinsuranceAcquisitionExpenses | 376.9 wtm_InsuranceAndReinsuranceAcquisitionExpenses | 430.2 wtm_InsuranceAndReinsuranceAcquisitionExpenses
Other underwriting expenses |  |  |  |  |  |  |  |  | 309.3 us-gaap_OtherUnderwritingExpense | 331.3 us-gaap_OtherUnderwritingExpense | 321.8 us-gaap_OtherUnderwritingExpense
General and administrative expenses |  |  |  |  |  |  |  |  | 288.2 us-gaap_GeneralAndAdministrativeExpense | 181.3 us-gaap_GeneralAndAdministrativeExpense | 182.2 us-gaap_GeneralAndAdministrativeExpense
Interest expense on debt |  |  |  |  |  |  |  |  | 41.9 us-gaap_InterestExpenseDebt | 42.5 us-gaap_InterestExpenseDebt | 44.8 us-gaap_InterestExpenseDebt
Expenses | 643.5 us-gaap_BenefitsLossesAndExpenses | 555.0 us-gaap_BenefitsLossesAndExpenses | 543.8 us-gaap_BenefitsLossesAndExpenses | 466.2 us-gaap_BenefitsLossesAndExpenses | 492.4 us-gaap_BenefitsLossesAndExpenses | 518.8 us-gaap_BenefitsLossesAndExpenses | 485.7 us-gaap_BenefitsLossesAndExpenses | 475.6 us-gaap_BenefitsLossesAndExpenses | 2,208.5 us-gaap_BenefitsLossesAndExpenses | 1,972.5 us-gaap_BenefitsLossesAndExpenses | 2,172.9 us-gaap_BenefitsLossesAndExpenses
Pre-tax loss | 46.2 us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments | 34.4 us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments | 109.0 us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments | 112.1 us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments | 134.2 us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments | 55.3 us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments | 3.6 us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments | 151.8 us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments | 301.7 us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments | 344.9 us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments | 262.8 us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments
OneBeacon |  |  |  |  |  |  |  |  |  |  |
Segment reporting information |  |  |  |  |  |  |  |  |  |  |
Earned insurance and reinsurance premiums |  |  |  |  |  |  |  |  | 1,177.1 us-gaap_PremiumsEarnedNet / us-gaap_StatementBusinessSegmentsAxis = wtm_OnebeaconMember | 1,120.4 us-gaap_PremiumsEarnedNet / us-gaap_StatementBusinessSegmentsAxis = wtm_OnebeaconMember | 1,132.0 us-gaap_PremiumsEarnedNet / us-gaap_StatementBusinessSegmentsAxis = wtm_OnebeaconMember
Net investment income |  |  |  |  |  |  |  |  | 41.7 us-gaap_NetInvestmentIncome / us-gaap_StatementBusinessSegmentsAxis = wtm_OnebeaconMember | 41.1 us-gaap_NetInvestmentIncome / us-gaap_StatementBusinessSegmentsAxis = wtm_OnebeaconMember | 53.6 us-gaap_NetInvestmentIncome / us-gaap_StatementBusinessSegmentsAxis = wtm_OnebeaconMember
Net investment income (loss) - surplus note interest |  |  |  |  |  |  |  |  | 0 wtm_NetInvestmentIncomeSurplusNotes / us-gaap_StatementBusinessSegmentsAxis = wtm_OnebeaconMember | 0 wtm_NetInvestmentIncomeSurplusNotes / us-gaap_StatementBusinessSegmentsAxis = wtm_OnebeaconMember | 0 wtm_NetInvestmentIncomeSurplusNotes / us-gaap_StatementBusinessSegmentsAxis = wtm_OnebeaconMember
Net realized and unrealized investment gains |  |  |  |  |  |  |  |  | 40.4 us-gaap_GainLossOnInvestments / us-gaap_StatementBusinessSegmentsAxis = wtm_OnebeaconMember | 49.4 us-gaap_GainLossOnInvestments / us-gaap_StatementBusinessSegmentsAxis = wtm_OnebeaconMember | 55.7 us-gaap_GainLossOnInvestments / us-gaap_StatementBusinessSegmentsAxis = wtm_OnebeaconMember
Other revenue |  |  |  |  |  |  |  |  | 5.8 us-gaap_OtherIncome / us-gaap_StatementBusinessSegmentsAxis = wtm_OnebeaconMember | 31.2 us-gaap_OtherIncome / us-gaap_StatementBusinessSegmentsAxis = wtm_OnebeaconMember | (0.5)us-gaap_OtherIncome / us-gaap_StatementBusinessSegmentsAxis = wtm_OnebeaconMember
Total revenues |  |  |  |  |  |  |  |  | 1,265.0 us-gaap_Revenues / us-gaap_StatementBusinessSegmentsAxis = wtm_OnebeaconMember | 1,242.1 us-gaap_Revenues / us-gaap_StatementBusinessSegmentsAxis = wtm_OnebeaconMember | 1,240.8 us-gaap_Revenues / us-gaap_StatementBusinessSegmentsAxis = wtm_OnebeaconMember
Loss and loss adjustment expenses |  |  |  |  |  |  |  |  | 815.1 us-gaap_PolicyholderBenefitsAndClaimsIncurredNet / us-gaap_StatementBusinessSegmentsAxis = wtm_OnebeaconMember | 622.1 us-gaap_PolicyholderBenefitsAndClaimsIncurredNet / us-gaap_StatementBusinessSegmentsAxis = wtm_OnebeaconMember | 650.0 us-gaap_PolicyholderBenefitsAndClaimsIncurredNet / us-gaap_StatementBusinessSegmentsAxis = wtm_OnebeaconMember
Insurance and reinsurance acquisition expenses |  |  |  |  |  |  |  |  | 203.3 wtm_InsuranceAndReinsuranceAcquisitionExpenses / us-gaap_StatementBusinessSegmentsAxis = wtm_OnebeaconMember | 208.9 wtm_InsuranceAndReinsuranceAcquisitionExpenses / us-gaap_StatementBusinessSegmentsAxis = wtm_OnebeaconMember | 249.4 wtm_InsuranceAndReinsuranceAcquisitionExpenses / us-gaap_StatementBusinessSegmentsAxis = wtm_OnebeaconMember
Other underwriting expenses |  |  |  |  |  |  |  |  | 179.2 us-gaap_OtherUnderwritingExpense / us-gaap_StatementBusinessSegmentsAxis = wtm_OnebeaconMember | 204.8 us-gaap_OtherUnderwritingExpense / us-gaap_StatementBusinessSegmentsAxis = wtm_OnebeaconMember | 205.2 us-gaap_OtherUnderwritingExpense / us-gaap_StatementBusinessSegmentsAxis = wtm_OnebeaconMember
General and administrative expenses |  |  |  |  |  |  |  |  | 13.8 us-gaap_GeneralAndAdministrativeExpense / us-gaap_StatementBusinessSegmentsAxis = wtm_OnebeaconMember | 12.0 us-gaap_GeneralAndAdministrativeExpense / us-gaap_StatementBusinessSegmentsAxis = wtm_OnebeaconMember | 13.4 us-gaap_GeneralAndAdministrativeExpense / us-gaap_StatementBusinessSegmentsAxis = wtm_OnebeaconMember
Interest expense on debt |  |  |  |  |  |  |  |  | 13.0 us-gaap_InterestExpenseDebt / us-gaap_StatementBusinessSegmentsAxis = wtm_OnebeaconMember | 13.0 us-gaap_InterestExpenseDebt / us-gaap_StatementBusinessSegmentsAxis = wtm_OnebeaconMember | 16.9 us-gaap_InterestExpenseDebt / us-gaap_StatementBusinessSegmentsAxis = wtm_OnebeaconMember
Expenses |  |  |  |  |  |  |  |  | 1,224.4 us-gaap_BenefitsLossesAndExpenses / us-gaap_StatementBusinessSegmentsAxis = wtm_OnebeaconMember | 1,060.8 us-gaap_BenefitsLossesAndExpenses / us-gaap_StatementBusinessSegmentsAxis = wtm_OnebeaconMember | 1,134.9 us-gaap_BenefitsLossesAndExpenses / us-gaap_StatementBusinessSegmentsAxis = wtm_OnebeaconMember
Pre-tax loss |  |  |  |  |  |  |  |  | 40.6 us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments / us-gaap_StatementBusinessSegmentsAxis = wtm_OnebeaconMember | 181.3 us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments / us-gaap_StatementBusinessSegmentsAxis = wtm_OnebeaconMember | 105.9 us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments / us-gaap_StatementBusinessSegmentsAxis = wtm_OnebeaconMember
Sirius Group |  |  |  |  |  |  |  |  |  |  |
Segment reporting information |  |  |  |  |  |  |  |  |  |  |
Earned insurance and reinsurance premiums |  |  |  |  |  |  |  |  | 873.9 us-gaap_PremiumsEarnedNet / us-gaap_StatementBusinessSegmentsAxis = wtm_SiriusGroupMember | 866.4 us-gaap_PremiumsEarnedNet / us-gaap_StatementBusinessSegmentsAxis = wtm_SiriusGroupMember | 931.6 us-gaap_PremiumsEarnedNet / us-gaap_StatementBusinessSegmentsAxis = wtm_SiriusGroupMember
Net investment income |  |  |  |  |  |  |  |  | 41.1 us-gaap_NetInvestmentIncome / us-gaap_StatementBusinessSegmentsAxis = wtm_SiriusGroupMember | 48.8 us-gaap_NetInvestmentIncome / us-gaap_StatementBusinessSegmentsAxis = wtm_SiriusGroupMember | 65.0 us-gaap_NetInvestmentIncome / us-gaap_StatementBusinessSegmentsAxis = wtm_SiriusGroupMember
Net investment income (loss) - surplus note interest |  |  |  |  |  |  |  |  | 0 wtm_NetInvestmentIncomeSurplusNotes / us-gaap_StatementBusinessSegmentsAxis = wtm_SiriusGroupMember | 0 wtm_NetInvestmentIncomeSurplusNotes / us-gaap_StatementBusinessSegmentsAxis = wtm_SiriusGroupMember | 0 wtm_NetInvestmentIncomeSurplusNotes / us-gaap_StatementBusinessSegmentsAxis = wtm_SiriusGroupMember
Net realized and unrealized investment gains |  |  |  |  |  |  |  |  | 209.2 us-gaap_GainLossOnInvestments / us-gaap_StatementBusinessSegmentsAxis = wtm_SiriusGroupMember | 26.7 us-gaap_GainLossOnInvestments / us-gaap_StatementBusinessSegmentsAxis = wtm_SiriusGroupMember | 17.3 us-gaap_GainLossOnInvestments / us-gaap_StatementBusinessSegmentsAxis = wtm_SiriusGroupMember
Other revenue |  |  |  |  |  |  |  |  | (62.4)us-gaap_OtherIncome / us-gaap_StatementBusinessSegmentsAxis = wtm_SiriusGroupMember | 16.8 us-gaap_OtherIncome / us-gaap_StatementBusinessSegmentsAxis = wtm_SiriusGroupMember | 70.6 us-gaap_OtherIncome / us-gaap_StatementBusinessSegmentsAxis = wtm_SiriusGroupMember
Total revenues |  |  |  |  |  |  |  |  | 1,061.8 us-gaap_Revenues / us-gaap_StatementBusinessSegmentsAxis = wtm_SiriusGroupMember | 958.7 us-gaap_Revenues / us-gaap_StatementBusinessSegmentsAxis = wtm_SiriusGroupMember | 1,084.5 us-gaap_Revenues / us-gaap_StatementBusinessSegmentsAxis = wtm_SiriusGroupMember
Loss and loss adjustment expenses |  |  |  |  |  |  |  |  | 345.3 us-gaap_PolicyholderBenefitsAndClaimsIncurredNet / us-gaap_StatementBusinessSegmentsAxis = wtm_SiriusGroupMember | 418.4 us-gaap_PolicyholderBenefitsAndClaimsIncurredNet / us-gaap_StatementBusinessSegmentsAxis = wtm_SiriusGroupMember | 543.9 us-gaap_PolicyholderBenefitsAndClaimsIncurredNet / us-gaap_StatementBusinessSegmentsAxis = wtm_SiriusGroupMember
Insurance and reinsurance acquisition expenses |  |  |  |  |  |  |  |  | 193.6 wtm_InsuranceAndReinsuranceAcquisitionExpenses / us-gaap_StatementBusinessSegmentsAxis = wtm_SiriusGroupMember | 166.5 wtm_InsuranceAndReinsuranceAcquisitionExpenses / us-gaap_StatementBusinessSegmentsAxis = wtm_SiriusGroupMember | 180.8 wtm_InsuranceAndReinsuranceAcquisitionExpenses / us-gaap_StatementBusinessSegmentsAxis = wtm_SiriusGroupMember
Other underwriting expenses |  |  |  |  |  |  |  |  | 129.7 us-gaap_OtherUnderwritingExpense / us-gaap_StatementBusinessSegmentsAxis = wtm_SiriusGroupMember | 126.1 us-gaap_OtherUnderwritingExpense / us-gaap_StatementBusinessSegmentsAxis = wtm_SiriusGroupMember | 116.4 us-gaap_OtherUnderwritingExpense / us-gaap_StatementBusinessSegmentsAxis = wtm_SiriusGroupMember
General and administrative expenses |  |  |  |  |  |  |  |  | 30.5 us-gaap_GeneralAndAdministrativeExpense / us-gaap_StatementBusinessSegmentsAxis = wtm_SiriusGroupMember | 32.2 us-gaap_GeneralAndAdministrativeExpense / us-gaap_StatementBusinessSegmentsAxis = wtm_SiriusGroupMember | 45.9 us-gaap_GeneralAndAdministrativeExpense / us-gaap_StatementBusinessSegmentsAxis = wtm_SiriusGroupMember
Interest expense on debt |  |  |  |  |  |  |  |  | 26.3 us-gaap_InterestExpenseDebt / us-gaap_StatementBusinessSegmentsAxis = wtm_SiriusGroupMember | 26.3 us-gaap_InterestExpenseDebt / us-gaap_StatementBusinessSegmentsAxis = wtm_SiriusGroupMember | 26.2 us-gaap_InterestExpenseDebt / us-gaap_StatementBusinessSegmentsAxis = wtm_SiriusGroupMember
Expenses |  |  |  |  |  |  |  |  | 725.4 us-gaap_BenefitsLossesAndExpenses / us-gaap_StatementBusinessSegmentsAxis = wtm_SiriusGroupMember | 769.5 us-gaap_BenefitsLossesAndExpenses / us-gaap_StatementBusinessSegmentsAxis = wtm_SiriusGroupMember | 913.2 us-gaap_BenefitsLossesAndExpenses / us-gaap_StatementBusinessSegmentsAxis = wtm_SiriusGroupMember
Pre-tax loss |  |  |  |  |  |  |  |  | 336.4 us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments / us-gaap_StatementBusinessSegmentsAxis = wtm_SiriusGroupMember | 189.2 us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments / us-gaap_StatementBusinessSegmentsAxis = wtm_SiriusGroupMember | 171.3 us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments / us-gaap_StatementBusinessSegmentsAxis = wtm_SiriusGroupMember
BAM |  |  |  |  |  |  |  |  |  |  |
Segment reporting information |  |  |  |  |  |  |  |  |  |  |
Earned insurance and reinsurance premiums |  |  |  |  |  |  |  |  | 0.4 us-gaap_PremiumsEarnedNet / us-gaap_StatementBusinessSegmentsAxis = wtm_BamMember | 0.1 us-gaap_PremiumsEarnedNet / us-gaap_StatementBusinessSegmentsAxis = wtm_BamMember | 0 us-gaap_PremiumsEarnedNet / us-gaap_StatementBusinessSegmentsAxis = wtm_BamMember
Net investment income |  |  |  |  |  |  |  |  | 5.7 us-gaap_NetInvestmentIncome / us-gaap_StatementBusinessSegmentsAxis = wtm_BamMember | 4.7 us-gaap_NetInvestmentIncome / us-gaap_StatementBusinessSegmentsAxis = wtm_BamMember | 1.9 us-gaap_NetInvestmentIncome / us-gaap_StatementBusinessSegmentsAxis = wtm_BamMember
Net investment income (loss) - surplus note interest |  |  |  |  |  |  |  |  | (15.7)wtm_NetInvestmentIncomeSurplusNotes / us-gaap_StatementBusinessSegmentsAxis = wtm_BamMember | (40.2)wtm_NetInvestmentIncomeSurplusNotes / us-gaap_StatementBusinessSegmentsAxis = wtm_BamMember | (18.4)wtm_NetInvestmentIncomeSurplusNotes / us-gaap_StatementBusinessSegmentsAxis = wtm_BamMember
Net realized and unrealized investment gains |  |  |  |  |  |  |  |  | 6.6 us-gaap_GainLossOnInvestments / us-gaap_StatementBusinessSegmentsAxis = wtm_BamMember | (9.3)us-gaap_GainLossOnInvestments / us-gaap_StatementBusinessSegmentsAxis = wtm_BamMember | 0 us-gaap_GainLossOnInvestments / us-gaap_StatementBusinessSegmentsAxis = wtm_BamMember
Other revenue |  |  |  |  |  |  |  |  | 0.6 us-gaap_OtherIncome / us-gaap_StatementBusinessSegmentsAxis = wtm_BamMember | 0.4 us-gaap_OtherIncome / us-gaap_StatementBusinessSegmentsAxis = wtm_BamMember | 0 us-gaap_OtherIncome / us-gaap_StatementBusinessSegmentsAxis = wtm_BamMember
Total revenues |  |  |  |  |  |  |  |  | (2.4)us-gaap_Revenues / us-gaap_StatementBusinessSegmentsAxis = wtm_BamMember | (44.3)us-gaap_Revenues / us-gaap_StatementBusinessSegmentsAxis = wtm_BamMember | (16.5)us-gaap_Revenues / us-gaap_StatementBusinessSegmentsAxis = wtm_BamMember
Loss and loss adjustment expenses |  |  |  |  |  |  |  |  | 0 us-gaap_PolicyholderBenefitsAndClaimsIncurredNet / us-gaap_StatementBusinessSegmentsAxis = wtm_BamMember | 0 us-gaap_PolicyholderBenefitsAndClaimsIncurredNet / us-gaap_StatementBusinessSegmentsAxis = wtm_BamMember | 0 us-gaap_PolicyholderBenefitsAndClaimsIncurredNet / us-gaap_StatementBusinessSegmentsAxis = wtm_BamMember
Insurance and reinsurance acquisition expenses |  |  |  |  |  |  |  |  | 1.8 wtm_InsuranceAndReinsuranceAcquisitionExpenses / us-gaap_StatementBusinessSegmentsAxis = wtm_BamMember | 1.4 wtm_InsuranceAndReinsuranceAcquisitionExpenses / us-gaap_StatementBusinessSegmentsAxis = wtm_BamMember | 0 wtm_InsuranceAndReinsuranceAcquisitionExpenses / us-gaap_StatementBusinessSegmentsAxis = wtm_BamMember
Other underwriting expenses |  |  |  |  |  |  |  |  | 0.4 us-gaap_OtherUnderwritingExpense / us-gaap_StatementBusinessSegmentsAxis = wtm_BamMember | 0.4 us-gaap_OtherUnderwritingExpense / us-gaap_StatementBusinessSegmentsAxis = wtm_BamMember | 0.2 us-gaap_OtherUnderwritingExpense / us-gaap_StatementBusinessSegmentsAxis = wtm_BamMember
General and administrative expenses |  |  |  |  |  |  |  |  | 35.9 us-gaap_GeneralAndAdministrativeExpense / us-gaap_StatementBusinessSegmentsAxis = wtm_BamMember | 32.5 us-gaap_GeneralAndAdministrativeExpense / us-gaap_StatementBusinessSegmentsAxis = wtm_BamMember | 19.6 us-gaap_GeneralAndAdministrativeExpense / us-gaap_StatementBusinessSegmentsAxis = wtm_BamMember
Interest expense on debt |  |  |  |  |  |  |  |  | 0 us-gaap_InterestExpenseDebt / us-gaap_StatementBusinessSegmentsAxis = wtm_BamMember | 0 us-gaap_InterestExpenseDebt / us-gaap_StatementBusinessSegmentsAxis = wtm_BamMember | 0 us-gaap_InterestExpenseDebt / us-gaap_StatementBusinessSegmentsAxis = wtm_BamMember
Expenses |  |  |  |  |  |  |  |  | 38.1 us-gaap_BenefitsLossesAndExpenses / us-gaap_StatementBusinessSegmentsAxis = wtm_BamMember | 34.3 us-gaap_BenefitsLossesAndExpenses / us-gaap_StatementBusinessSegmentsAxis = wtm_BamMember | 19.8 us-gaap_BenefitsLossesAndExpenses / us-gaap_StatementBusinessSegmentsAxis = wtm_BamMember
Pre-tax loss |  |  |  |  |  |  |  |  | (40.5)us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments / us-gaap_StatementBusinessSegmentsAxis = wtm_BamMember | (78.6)us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments / us-gaap_StatementBusinessSegmentsAxis = wtm_BamMember | (36.3)us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments / us-gaap_StatementBusinessSegmentsAxis = wtm_BamMember
Other Segments |  |  |  |  |  |  |  |  |  |  |
Segment reporting information |  |  |  |  |  |  |  |  |  |  |
Earned insurance and reinsurance premiums |  |  |  |  |  |  |  |  | 6.1 us-gaap_PremiumsEarnedNet / us-gaap_StatementBusinessSegmentsAxis = us-gaap_AllOtherSegmentsMember | 0 us-gaap_PremiumsEarnedNet / us-gaap_StatementBusinessSegmentsAxis = us-gaap_AllOtherSegmentsMember | 0 us-gaap_PremiumsEarnedNet / us-gaap_StatementBusinessSegmentsAxis = us-gaap_AllOtherSegmentsMember
Net investment income |  |  |  |  |  |  |  |  | 15.1 us-gaap_NetInvestmentIncome / us-gaap_StatementBusinessSegmentsAxis = us-gaap_AllOtherSegmentsMember | 15.3 us-gaap_NetInvestmentIncome / us-gaap_StatementBusinessSegmentsAxis = us-gaap_AllOtherSegmentsMember | 32.8 us-gaap_NetInvestmentIncome / us-gaap_StatementBusinessSegmentsAxis = us-gaap_AllOtherSegmentsMember
Net investment income (loss) - surplus note interest |  |  |  |  |  |  |  |  | 0 wtm_NetInvestmentIncomeSurplusNotes / us-gaap_StatementBusinessSegmentsAxis = us-gaap_AllOtherSegmentsMember | 0 wtm_NetInvestmentIncomeSurplusNotes / us-gaap_StatementBusinessSegmentsAxis = us-gaap_AllOtherSegmentsMember | 0 wtm_NetInvestmentIncomeSurplusNotes / us-gaap_StatementBusinessSegmentsAxis = us-gaap_AllOtherSegmentsMember
Net realized and unrealized investment gains |  |  |  |  |  |  |  |  | 26.0 us-gaap_GainLossOnInvestments / us-gaap_StatementBusinessSegmentsAxis = us-gaap_AllOtherSegmentsMember | 96.9 us-gaap_GainLossOnInvestments / us-gaap_StatementBusinessSegmentsAxis = us-gaap_AllOtherSegmentsMember | 45.2 us-gaap_GainLossOnInvestments / us-gaap_StatementBusinessSegmentsAxis = us-gaap_AllOtherSegmentsMember
Other revenue |  |  |  |  |  |  |  |  | 118.4 us-gaap_OtherIncome / us-gaap_StatementBusinessSegmentsAxis = us-gaap_AllOtherSegmentsMember | 9.1 us-gaap_OtherIncome / us-gaap_StatementBusinessSegmentsAxis = us-gaap_AllOtherSegmentsMember | 30.2 us-gaap_OtherIncome / us-gaap_StatementBusinessSegmentsAxis = us-gaap_AllOtherSegmentsMember
Total revenues |  |  |  |  |  |  |  |  | 165.6 us-gaap_Revenues / us-gaap_StatementBusinessSegmentsAxis = us-gaap_AllOtherSegmentsMember | 121.3 us-gaap_Revenues / us-gaap_StatementBusinessSegmentsAxis = us-gaap_AllOtherSegmentsMember | 108.2 us-gaap_Revenues / us-gaap_StatementBusinessSegmentsAxis = us-gaap_AllOtherSegmentsMember
Loss and loss adjustment expenses |  |  |  |  |  |  |  |  | 8.9 us-gaap_PolicyholderBenefitsAndClaimsIncurredNet / us-gaap_StatementBusinessSegmentsAxis = us-gaap_AllOtherSegmentsMember | 0 us-gaap_PolicyholderBenefitsAndClaimsIncurredNet / us-gaap_StatementBusinessSegmentsAxis = us-gaap_AllOtherSegmentsMember | 0 us-gaap_PolicyholderBenefitsAndClaimsIncurredNet / us-gaap_StatementBusinessSegmentsAxis = us-gaap_AllOtherSegmentsMember
Insurance and reinsurance acquisition expenses |  |  |  |  |  |  |  |  | 0.8 wtm_InsuranceAndReinsuranceAcquisitionExpenses / us-gaap_StatementBusinessSegmentsAxis = us-gaap_AllOtherSegmentsMember | 0 wtm_InsuranceAndReinsuranceAcquisitionExpenses / us-gaap_StatementBusinessSegmentsAxis = us-gaap_AllOtherSegmentsMember | 0 wtm_InsuranceAndReinsuranceAcquisitionExpenses / us-gaap_StatementBusinessSegmentsAxis = us-gaap_AllOtherSegmentsMember
Other underwriting expenses |  |  |  |  |  |  |  |  | 0 us-gaap_OtherUnderwritingExpense / us-gaap_StatementBusinessSegmentsAxis = us-gaap_AllOtherSegmentsMember | 0 us-gaap_OtherUnderwritingExpense / us-gaap_StatementBusinessSegmentsAxis = us-gaap_AllOtherSegmentsMember | 0 us-gaap_OtherUnderwritingExpense / us-gaap_StatementBusinessSegmentsAxis = us-gaap_AllOtherSegmentsMember
General and administrative expenses |  |  |  |  |  |  |  |  | 206.4 us-gaap_GeneralAndAdministrativeExpense / us-gaap_StatementBusinessSegmentsAxis = us-gaap_AllOtherSegmentsMember | 103.2 us-gaap_GeneralAndAdministrativeExpense / us-gaap_StatementBusinessSegmentsAxis = us-gaap_AllOtherSegmentsMember | 98.8 us-gaap_GeneralAndAdministrativeExpense / us-gaap_StatementBusinessSegmentsAxis = us-gaap_AllOtherSegmentsMember
Interest expense on debt |  |  |  |  |  |  |  |  | 2.6 us-gaap_InterestExpenseDebt / us-gaap_StatementBusinessSegmentsAxis = us-gaap_AllOtherSegmentsMember | 3.2 us-gaap_InterestExpenseDebt / us-gaap_StatementBusinessSegmentsAxis = us-gaap_AllOtherSegmentsMember | 1.7 us-gaap_InterestExpenseDebt / us-gaap_StatementBusinessSegmentsAxis = us-gaap_AllOtherSegmentsMember
Expenses |  |  |  |  |  |  |  |  | 218.7 us-gaap_BenefitsLossesAndExpenses / us-gaap_StatementBusinessSegmentsAxis = us-gaap_AllOtherSegmentsMember | 106.4 us-gaap_BenefitsLossesAndExpenses / us-gaap_StatementBusinessSegmentsAxis = us-gaap_AllOtherSegmentsMember | 100.5 us-gaap_BenefitsLossesAndExpenses / us-gaap_StatementBusinessSegmentsAxis = us-gaap_AllOtherSegmentsMember
Pre-tax loss |  |  |  |  |  |  |  |  | (53.1)us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments / us-gaap_StatementBusinessSegmentsAxis = us-gaap_AllOtherSegmentsMember | 14.9 us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments / us-gaap_StatementBusinessSegmentsAxis = us-gaap_AllOtherSegmentsMember | 7.7 us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments / us-gaap_StatementBusinessSegmentsAxis = us-gaap_AllOtherSegmentsMember
HG Global |  |  |  |  |  |  |  |  |  |  |
Segment reporting information |  |  |  |  |  |  |  |  |  |  |
Percentage of par value of policy reinsured | 15.00%wtm_PercentageOfParValueOfPolicyReinsured / us-gaap_StatementBusinessSegmentsAxis = wtm_HgGlobalMember |  |  |  |  |  |  |  | 15.00%wtm_PercentageOfParValueOfPolicyReinsured / us-gaap_StatementBusinessSegmentsAxis = wtm_HgGlobalMember |  |
Earned insurance and reinsurance premiums |  |  |  |  |  |  |  |  | 1.4 us-gaap_PremiumsEarnedNet / us-gaap_StatementBusinessSegmentsAxis = wtm_HgGlobalMember | 0.4 us-gaap_PremiumsEarnedNet / us-gaap_StatementBusinessSegmentsAxis = wtm_HgGlobalMember | 0 us-gaap_PremiumsEarnedNet / us-gaap_StatementBusinessSegmentsAxis = wtm_HgGlobalMember
Net investment income |  |  |  |  |  |  |  |  | 1.4 us-gaap_NetInvestmentIncome / us-gaap_StatementBusinessSegmentsAxis = wtm_HgGlobalMember | 1.0 us-gaap_NetInvestmentIncome / us-gaap_StatementBusinessSegmentsAxis = wtm_HgGlobalMember | 0.3 us-gaap_NetInvestmentIncome / us-gaap_StatementBusinessSegmentsAxis = wtm_HgGlobalMember
Net investment income (loss) - surplus note interest |  |  |  |  |  |  |  |  | 15.7 wtm_NetInvestmentIncomeSurplusNotes / us-gaap_StatementBusinessSegmentsAxis = wtm_HgGlobalMember | 40.2 wtm_NetInvestmentIncomeSurplusNotes / us-gaap_StatementBusinessSegmentsAxis = wtm_HgGlobalMember | 18.4 wtm_NetInvestmentIncomeSurplusNotes / us-gaap_StatementBusinessSegmentsAxis = wtm_HgGlobalMember
Net realized and unrealized investment gains |  |  |  |  |  |  |  |  | 1.7 us-gaap_GainLossOnInvestments / us-gaap_StatementBusinessSegmentsAxis = wtm_HgGlobalMember | (2.0)us-gaap_GainLossOnInvestments / us-gaap_StatementBusinessSegmentsAxis = wtm_HgGlobalMember | 0 us-gaap_GainLossOnInvestments / us-gaap_StatementBusinessSegmentsAxis = wtm_HgGlobalMember
Other revenue |  |  |  |  |  |  |  |  | 0 us-gaap_OtherIncome / us-gaap_StatementBusinessSegmentsAxis = wtm_HgGlobalMember | 0 us-gaap_OtherIncome / us-gaap_StatementBusinessSegmentsAxis = wtm_HgGlobalMember | 0 us-gaap_OtherIncome / us-gaap_StatementBusinessSegmentsAxis = wtm_HgGlobalMember
Total revenues |  |  |  |  |  |  |  |  | 20.2 us-gaap_Revenues / us-gaap_StatementBusinessSegmentsAxis = wtm_HgGlobalMember | 39.6 us-gaap_Revenues / us-gaap_StatementBusinessSegmentsAxis = wtm_HgGlobalMember | 18.7 us-gaap_Revenues / us-gaap_StatementBusinessSegmentsAxis = wtm_HgGlobalMember
Loss and loss adjustment expenses |  |  |  |  |  |  |  |  | 0 us-gaap_PolicyholderBenefitsAndClaimsIncurredNet / us-gaap_StatementBusinessSegmentsAxis = wtm_HgGlobalMember | 0 us-gaap_PolicyholderBenefitsAndClaimsIncurredNet / us-gaap_StatementBusinessSegmentsAxis = wtm_HgGlobalMember | 0 us-gaap_PolicyholderBenefitsAndClaimsIncurredNet / us-gaap_StatementBusinessSegmentsAxis = wtm_HgGlobalMember
Insurance and reinsurance acquisition expenses |  |  |  |  |  |  |  |  | 0.3 wtm_InsuranceAndReinsuranceAcquisitionExpenses / us-gaap_StatementBusinessSegmentsAxis = wtm_HgGlobalMember | 0.1 wtm_InsuranceAndReinsuranceAcquisitionExpenses / us-gaap_StatementBusinessSegmentsAxis = wtm_HgGlobalMember | 0 wtm_InsuranceAndReinsuranceAcquisitionExpenses / us-gaap_StatementBusinessSegmentsAxis = wtm_HgGlobalMember
Other underwriting expenses |  |  |  |  |  |  |  |  | 0 us-gaap_OtherUnderwritingExpense / us-gaap_StatementBusinessSegmentsAxis = wtm_HgGlobalMember | 0 us-gaap_OtherUnderwritingExpense / us-gaap_StatementBusinessSegmentsAxis = wtm_HgGlobalMember | 0 us-gaap_OtherUnderwritingExpense / us-gaap_StatementBusinessSegmentsAxis = wtm_HgGlobalMember
General and administrative expenses |  |  |  |  |  |  |  |  | 1.6 us-gaap_GeneralAndAdministrativeExpense / us-gaap_StatementBusinessSegmentsAxis = wtm_HgGlobalMember | 1.4 us-gaap_GeneralAndAdministrativeExpense / us-gaap_StatementBusinessSegmentsAxis = wtm_HgGlobalMember | 4.5 us-gaap_GeneralAndAdministrativeExpense / us-gaap_StatementBusinessSegmentsAxis = wtm_HgGlobalMember
Interest expense on debt |  |  |  |  |  |  |  |  | 0 us-gaap_InterestExpenseDebt / us-gaap_StatementBusinessSegmentsAxis = wtm_HgGlobalMember | 0 us-gaap_InterestExpenseDebt / us-gaap_StatementBusinessSegmentsAxis = wtm_HgGlobalMember | 0 us-gaap_InterestExpenseDebt / us-gaap_StatementBusinessSegmentsAxis = wtm_HgGlobalMember
Expenses |  |  |  |  |  |  |  |  | 1.9 us-gaap_BenefitsLossesAndExpenses / us-gaap_StatementBusinessSegmentsAxis = wtm_HgGlobalMember | 1.5 us-gaap_BenefitsLossesAndExpenses / us-gaap_StatementBusinessSegmentsAxis = wtm_HgGlobalMember | 4.5 us-gaap_BenefitsLossesAndExpenses / us-gaap_StatementBusinessSegmentsAxis = wtm_HgGlobalMember
Pre-tax loss |  |  |  |  |  |  |  |  | $ 18.3 us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments / us-gaap_StatementBusinessSegmentsAxis = wtm_HgGlobalMember | $ 38.1 us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments / us-gaap_StatementBusinessSegmentsAxis = wtm_HgGlobalMember | $ 14.2 us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments / us-gaap_StatementBusinessSegmentsAxis = wtm_HgGlobalMember

X
- Definition The total amount of expense recognized during the period for future policy benefits, claims and claims adjustment costs, and for selling, general and administrative costs. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 225 -Section S99 -Paragraph 1 -Subparagraph (SX 210.7-04.5,6,7) -URI http://asc.fasb.org/extlink&oid=6879464&loc=d3e573970-122913 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 04 -Paragraph 5, 6, 7 -Article 7 + Details
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- Definition This item represents the net total realized and unrealized gain (loss) included in earnings for the period as a result of selling or holding marketable securities categorized as trading, available-for-sale, or held-to-maturity, including the unrealized holding gain (loss) of held-to-maturity securities transferred to the trading security category and the cumulative unrealized gain (loss) which was included in other comprehensive income (a separate component of shareholders' equity) for available-for-sale securities transferred to trading securities during the period. Additionally, this item would include any gains (losses) realized during the period from the sale of investments accounted for under the cost method of accounting and losses recognized for other than temporary impairments (OTTI) of the subject investments. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 28 -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3602-108585 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 225 -SubTopic 10 -Section S99 -Paragraph 2 -Subparagraph (SX 210.5-03.7(c),9(a)) -URI http://asc.fasb.org/extlink&oid=26872669&loc=d3e20235-122688 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 10 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=27724398&loc=d3e27405-111563 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 03 -Paragraph 7 -Article 5 Reference 5: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 9 -Subparagraph (c)-(e) -URI http://asc.fasb.org/extlink&oid=27724398&loc=d3e27357-111563 + Details
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- Definition The aggregate total of expenses of managing and administering the affairs of an entity, including affiliates of the reporting entity, which are not directly or indirectly associated with the manufacture, sale or creation of a product or product line. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 225 -SubTopic 10 -Section S99 -Paragraph 2 -Subparagraph (SX 210.5-03.4) -URI http://asc.fasb.org/extlink&oid=26872669&loc=d3e20235-122688 + Details
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- Definition Sum of operating profit and nonoperating income or expense before Income or Loss from equity method investments, income taxes, extraordinary items, and noncontrolling interest. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 235 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.4-08.(h)(1)(i)) -URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e23780-122690 + Details
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- Definition Amount of the cost of borrowed funds accounted for as interest expense for debt. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 225 -SubTopic 10 -Section S99 -Paragraph 2 -Subparagraph (SX 210.5-03.8) -URI http://asc.fasb.org/extlink&oid=26872669&loc=d3e20235-122688 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 03 -Paragraph 8 -Article 5 + Details
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- Definition Amount, after investment expense, of income earned from investments in securities and real estate. Includes, but is not limited to, real estate investment, policy loans, dividends, and interest. Excludes realized gain (loss) on investments. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 16 -Article 12 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 225 -Section S99 -Paragraph 1 -Subparagraph (SX 210.7-04.2) -URI http://asc.fasb.org/extlink&oid=6879464&loc=d3e573970-122913 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 04 -Paragraph 2 -Article 7 + Details
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- Definition Reflects the sum of all other revenue and income recognized by the entity in the period not otherwise specified in the income statement. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 225 -Section S99 -Paragraph 1 -Subparagraph (SX 210.7-04.4) -URI http://asc.fasb.org/extlink&oid=6879464&loc=d3e573970-122913 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 04 -Paragraph 4 -Article 7 + Details
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- Definition Costs incurred during the period, such as those relating to general administration and policy maintenance that do not vary with and are not primarily related to the acquisition or renewal of insurance contracts. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 04 -Paragraph 7 -Article 7 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 225 -Section S99 -Paragraph 1 -Subparagraph (SX 210.7-04.7) -URI http://asc.fasb.org/extlink&oid=6879464&loc=d3e573970-122913 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 720 -Section 25 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=6968134&loc=d3e28434-158551 + Details
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- Definition Amount, after effects of policies assumed or ceded, of expense related to the provision for policy benefits and costs incurred. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 225 -Section S99 -Paragraph 1 -Subparagraph (SX 210.7-04.5) -URI http://asc.fasb.org/extlink&oid=6879464&loc=d3e573970-122913 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 04 -Paragraph 5 -Article 7 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 20 -Section 50 -Paragraph 3 -URI http://asc.fasb.org/extlink&oid=6480758&loc=d3e6811-158387 + Details
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