XML 181 R126.htm IDEA: XBRL DOCUMENT
v2.4.0.8

Retirement and Postretirement Plans (Cash Flow) (Details) (USD $) |  |  |  | 12 Months Ended |  |  | 12 Months Ended |
--- | --- | --- | --- | --- | --- | --- | --- | ---
Dec. 31, 2013 | Dec. 31, 2012 | Dec. 31, 2011 | Dec. 31, 2014 OneBeacon Ltd. | Dec. 31, 2013 OneBeacon Ltd. | Dec. 31, 2013 OneBeacon | Dec. 31, 2012 OneBeacon | Dec. 31, 2013 Sirius Group | Dec. 31, 2012 Sirius Group | Dec. 31, 2011 Sirius Group | Dec. 31, 2013 Government Pension Plans [Member] Sirius Group | Dec. 31, 2012 Government Pension Plans [Member] Sirius Group | Dec. 31, 2011 Government Pension Plans [Member] Sirius Group | Dec. 31, 2013 Defined Contribution Plan [Member] Sirius Group | Dec. 31, 2012 Defined Contribution Plan [Member] Sirius Group | Dec. 31, 2011 Defined Contribution Plan [Member] Sirius Group | Dec. 31, 2013 Combination One [Member] Defined Contribution Plan [Member] Sirius Group | Dec. 31, 2013 Combination Two [Member] Defined Contribution Plan [Member] Sirius Group | Dec. 31, 2013 Maximum Sirius Group | Dec. 31, 2013 Maximum Defined Contribution Plan [Member] Sirius Group | Dec. 31, 2013 Minimum Defined Contribution Plan [Member] Sirius Group | Dec. 31, 2013 One Beacon Employee Stock Ownership Plan | Dec. 31, 2012 One Beacon Employee Stock Ownership Plan | Dec. 31, 2011 One Beacon Employee Stock Ownership Plan | Dec. 31, 2013 One Beacon Employee Stock Ownership Plan OneBeacon | Dec. 31, 2012 One Beacon Employee Stock Ownership Plan OneBeacon | Dec. 31, 2011 One Beacon Employee Stock Ownership Plan OneBeacon | Dec. 31, 2013 IRS OneBeacon | Dec. 31, 2013 IRS Sirius Group
Expected Benefit Payments |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
2014 |  |  |  |  | $ 5,100,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
2015 |  |  |  |  | 5,400,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
2016 |  |  |  |  | 5,600,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
2017 |  |  |  |  | 5,800,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
2018 |  |  |  |  | 6,100,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
2019-2023 |  |  |  |  | 33,900,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Employee savings plan |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Defined Contribution Plan, Employer Matching Contribution, Percent of Match |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 100.00% | 50.00% |  |  |  | 50.00% |  |  |  |
Defined Contribution Plan, Employer Matching Contribution, Percent of Employees' Gross Pay |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 2.00% | 4.00% |  |  |  |  |  |  | 6.00% |  |  |  |
Defined Contribution Plan, Cost Recognized |  |  |  |  |  |  |  | 700,000 | 400,000 | 300,000 | 9,700,000 | 7,500,000 | 9,600,000 | 600,000 | 600,000 | 700,000 |  |  |  |  |  | 6,300,000 | 4,800,000 | 6,300,000 | 2,300,000 | 2,800,000 | 3,000,000 |  |
Anticipated contribution to plan |  |  |  | 2,200,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Annual base contribution provided to participants expressed as percentage of salary |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 3.00% |  |  |  |  |  |  |
Social security wage base amount maximum |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 113,700 |  |  |  |  |  |  |
Variable contribution provided to participants (as percentage) |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 6.00% |  |  |  |  |  |  |
Employer matching contribution variable contributions |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 7.00% |  |  |  |  |  |  |  |  |  |
Deferred Benefit Plan Compensation Limits |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 255,000 | 255,000
Defined Benefit Plan, Benefit Obligation | 102,900,000 | 119,500,000 | 113,000,000 |  |  |  |  |  |  |  | 13,100,000 | 12,400,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Funded status at end of year | 39,900,000 | 5,200,000 |  |  |  |  |  |  |  |  | 1,000,000 | 1,700,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Post-employment benefit liability |  |  |  |  |  | $ 5,800,000 | $ 7,100,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |

X
- Definition 1) For defined benefit pension plans, the benefit obligation is the projected benefit obligation, which is the actuarial present value as of a date of all benefits attributed by the pension benefit formula to employee service rendered prior to that date. 2) For other postretirement defined benefit plans, the benefit obligation is the accumulated postretirement benefit obligation, which is the actuarial present value of benefits attributed to employee service rendered to a particular date. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=28361610&loc=d3e1928-114920 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Projected Benefit Obligation -URI http://asc.fasb.org/extlink&oid=6522206 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Accumulated Postretirement Benefit Obligation -URI http://asc.fasb.org/extlink&oid=6503904 + Details
Name: | us-gaap_DefinedBenefitPlanBenefitObligation
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

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

X
- Definition Amount of benefits expected to be paid in the five fiscal years after the fifth fiscal year following the latest fiscal year from a defined benefit plan. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (f) -URI http://asc.fasb.org/extlink&oid=28361610&loc=d3e1928-114920 + Details
Name: | us-gaap_DefinedBenefitPlanExpectedFutureBenefitPaymentsFiveFiscalYearsThereafter
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Amount of benefits expected to be paid in the next fiscal year following the latest fiscal year from a defined benefit plan. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (f) -URI http://asc.fasb.org/extlink&oid=28361610&loc=d3e1928-114920 + Details
Name: | us-gaap_DefinedBenefitPlanExpectedFutureBenefitPaymentsNextTwelveMonths
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Amount of benefits expected to be paid in the fifth fiscal year following the latest fiscal year from a defined benefit plan. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (f) -URI http://asc.fasb.org/extlink&oid=28361610&loc=d3e1928-114920 + Details
Name: | us-gaap_DefinedBenefitPlanExpectedFutureBenefitPaymentsYearFive
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Amount of benefits expected to be paid in the fourth fiscal year following the latest fiscal year from a defined benefit plan. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (f) -URI http://asc.fasb.org/extlink&oid=28361610&loc=d3e1928-114920 + Details
Name: | us-gaap_DefinedBenefitPlanExpectedFutureBenefitPaymentsYearFour
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Amount of benefits expected to be paid in the third fiscal year following the latest fiscal year from a defined benefit plan. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (f) -URI http://asc.fasb.org/extlink&oid=28361610&loc=d3e1928-114920 + Details
Name: | us-gaap_DefinedBenefitPlanExpectedFutureBenefitPaymentsYearThree
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Amount of benefits expected to be paid in the second fiscal year following the latest fiscal year from a defined benefit plan. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (f) -URI http://asc.fasb.org/extlink&oid=28361610&loc=d3e1928-114920 + Details
Name: | us-gaap_DefinedBenefitPlanExpectedFutureBenefitPaymentsYearTwo
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition The funded status is measured as the difference between the fair value of plan assets and the benefit obligation. Will normally be the same as the net Defined Benefit Plan, Amounts Recognized in Balance Sheet, Total. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=28361610&loc=d3e1928-114920 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 45 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=21915240&loc=d3e1703-114919 + Details
Name: | us-gaap_DefinedBenefitPlanFundedStatusOfPlan
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Amount of employer's best estimate of contributions expected to be paid to the plan during the next fiscal year beginning after the date of the latest statement of financial position. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (g) -URI http://asc.fasb.org/extlink&oid=28361610&loc=d3e1928-114920 + Details
Name: | us-gaap_DefinedBenefitPlansEstimatedFutureEmployerContributionsInNextFiscalYear
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition The amount of the cost recognized during the period for defined contribution plans. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 70 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6414718&loc=d3e28014-114942 + Details
Name: | us-gaap_DefinedContributionPlanCostRecognized
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Percentage of employees' gross pay for which the employer contributes a matching contribution to a defined contribution plan. + References No definition available. + Details
Name: | us-gaap_DefinedContributionPlanEmployerMatchingContributionPercent
Namespace Prefix: | us-gaap_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition Percentage employer matches of the employee's percentage contribution matched. + References No definition available. + Details
Name: | us-gaap_DefinedContributionPlanEmployerMatchingContributionPercentOfMatch
Namespace Prefix: | us-gaap_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition For a classified balance sheet, the carrying amount as of the balance sheet date of the portion of the obligations recognized for the various benefits provided to former or inactive employees, their beneficiaries, and covered dependents after employment but before retirement that is payable after one year (or beyond the operating cycle if longer). + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 712 -SubTopic 10 -Section 25 -Paragraph 4 -URI http://asc.fasb.org/extlink&oid=6410138&loc=d3e79691-111665 + Details
Name: | us-gaap_PostemploymentBenefitsLiabilityNoncurrent
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Defined Benefit Plan Compensation LImits + References No definition available. + Details
Name: | wtm_DefinedBenefitPlanCompensationLImits
Namespace Prefix: | wtm_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Defined Contribution Plan, Employer Matching Contribution, Variable Contributions + References No definition available. + Details
Name: | wtm_DefinedContributionPlanEmployerMatchingContributionVariableContributions
Namespace Prefix: | wtm_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition Represents the employer's annual contribution (as a percentage of salary up to the Social Security wage base) to the ESOP plan. + References No definition available. + Details
Name: | wtm_EmployeeStockOwnershipPlanEsopAnnualBaseContributionProvidedToParticipantsExpressedAsPercentageOfSalary
Namespace Prefix: | wtm_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition Represent the amount of contributed by the employee maximum amount applicable to social security wage base. + References No definition available. + Details
Name: | wtm_EmployeeStockOwnershipPlanEsopSocialSecurityWageBaseAmountMaximum
Namespace Prefix: | wtm_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Represents the employer's maximum annual variable contribution (as a percentage of salary up to the Social Security wage base) to the ESOP plan for employees who are not otherwise eligible for certain incentive compensation benefits. + References No definition available. + Details
Name: | wtm_EmployeeStockOwnershipPlanEsopVariableContributionProvidedToParticipantsNotEligibleToCertainBenefitsExpressedAsPercentageOfSalary
Namespace Prefix: | wtm_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

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