XML 101 R91.htm IDEA: XBRL DOCUMENT
v3.22.2

Employee Share-Based Incentive Compensation Plans - Performance Shares Granted Under the WTM Incentive Plan (Details) - Performance Share - W T M Incentive Plan - USD ($) $ in Millions | Jun. 30, 2022 | Mar. 31, 2022 | Dec. 31, 2021 | Jun. 30, 2021 | Mar. 31, 2021 | Dec. 31, 2020
--- | --- | --- | --- | --- | --- | ---
Share-based compensation arrangement by share-based payment award |  |  |  |  |  |
Target performance shares outstanding (in shares) | 40,050 |  |  |  |  |
Assumed forfeitures (in shares) | (601) |  |  |  |  |
Total target performance shares outstanding (in shares) | 39,449 | 39,302 | 40,828 | 41,252 | 40,784 | 42,458
Accrued Expense | $ 41.9 |  |  |  |  |
Assumed forfeitures | (0.7) |  |  |  |  |
Total Accrued Expense | $ 41.2 | $ 21.9 | $ 42.2 | $ 45.7 | $ 38.2 | $ 56.3
2020 – 2022 |  |  |  |  |  |
Share-based compensation arrangement by share-based payment award |  |  |  |  |  |
Target performance shares outstanding (in shares) | 13,350 |  |  |  |  |
Accrued Expense | $ 27.4 |  |  |  |  |
2021 – 2023 |  |  |  |  |  |
Share-based compensation arrangement by share-based payment award |  |  |  |  |  |
Target performance shares outstanding (in shares) | 13,475 |  |  |  |  |
Accrued Expense | $ 11.0 |  |  |  |  |
2022 – 2024 |  |  |  |  |  |
Share-based compensation arrangement by share-based payment award |  |  |  |  |  |
Target performance shares outstanding (in shares) | 13,225 |  |  |  |  |
Accrued Expense | $ 3.5 |  |  |  |  |

X
- Definition The number of non-vested equity-based payment instruments, excluding stock (or unit) options, that validly exist and are outstanding as of the balance sheet date. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c)(2)(ii) -URI https://asc.fasb.org/extlink&oid=128089324&loc=d3e5070-113901 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c)(2)(i) -URI https://asc.fasb.org/extlink&oid=128089324&loc=d3e5070-113901 + Details
Name: | us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber
Namespace Prefix: | us-gaap_
Data Type: | xbrli:sharesItemType
Balance Type: | na
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_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Aggregate carrying value as of the balance sheet date of liabilities for incentive compensation arrangements. + References No definition available. + Details
Name: | wtm_IncentiveCompensationPayable
Namespace Prefix: | wtm_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Carrying value as of the balance sheet date for performance shares before forfeitures. + References No definition available. + Details
Name: | wtm_IncentiveCompensationPayableBeforeForfeitures
Namespace Prefix: | wtm_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition This element represents the reduction for assumed forfeitures to the number of performance shares outstanding. + References No definition available. + Details
Name: | wtm_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsAssumedForfeitures
Namespace Prefix: | wtm_
Data Type: | xbrli:sharesItemType
Balance Type: | na
Period Type: | instant

X
- Definition This element represents the reduction to accrued expense for assumed forfeitures of performance shares. + References No definition available. + Details
Name: | wtm_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsAssumedForfeituresAmount
Namespace Prefix: | wtm_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition This element represents the number of non-vested performance shares before forfeiture assumptions. + References No definition available. + Details
Name: | wtm_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumberBeforeForfeitures
Namespace Prefix: | wtm_
Data Type: | xbrli:sharesItemType
Balance Type: | na
Period Type: | instant

X
- Details
Name: | us-gaap_AwardTypeAxis=us-gaap_PerformanceSharesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_PlanNameAxis=wtm_WTMIncentivePlanMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | wtm_ShareBasedCompensationArrangementByPerformanceSharesAwardPerformanceCycleAxis=wtm_RangeOfPerformanceCyclePreviousYearMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | wtm_ShareBasedCompensationArrangementByPerformanceSharesAwardPerformanceCycleAxis=wtm_PerformanceCyclePeriodTwoMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | wtm_ShareBasedCompensationArrangementByPerformanceSharesAwardPerformanceCycleAxis=wtm_PerformanceCyclePeriodThreeMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |