XML 64 R52.htm IDEA: XBRL DOCUMENT
v3.24.1.u1

Life and Annuity Benefits (Liability for Future Policy Benefit, Activity) (Details) - USD ($) $ in Thousands | 3 Months Ended |  |
--- | --- | --- | ---
Mar. 31, 2024 | Mar. 31, 2023 | Dec. 31, 2023 | Dec. 31, 2022
Liability for Future Policy Benefits Activity [Abstract] |  |  |  |  |
Liability for future policyholder benefits, beginning of year |  | $ 557,763 | $ 554,366 |  |
Liability for future policyholder benefits at original discount rate, beginning of year |  | 642,877 | 667,761 |  |
Effect of changes in cash flow assumptions |  |  |  | $ 0 | $ 0
Effect of actual variances from expected experience |  |  |  | 0 | $ 0
Adjusted liability for future policyholder benefits, beginning of year |  | 642,877 | 667,761 |  |
Interest accretion |  | 3,605 | 3,815 |  |
Benefit payments |  | (13,290) | (13,283) |  |
Effect of foreign currency changes |  | (11,706) | 10,396 |  |
Liability for future policy holder benefits t original discount rate, end of period |  | 621,486 | 668,689 |  |
Cumulative effect of changes in discount rate assumptions |  | (93,237) | (101,938) |  |
Liability for future policyholder benefits, beginning of year, ending of period | [1] | 528,249 | $ 566,751 |  |
Undiscounted liability for future policyholder benefits |  | $ 796,800 |  | $ 862,700 |
[1] | The undiscounted liability for future policyholder benefits was $796.8 million and $862.7 million as of March 31, 2024 and 2023, respectively.

X
- Definition Liability for Future Policy Benefit, Expected Future Policy Benefit, Effect of Foreign Currency Rate Changes + References No definition available. + Details
Name: | mkl_LiabilityForFuturePolicyBenefitExpectedFuturePolicyBenefitEffectOfForeignCurrencyRateChanges
Namespace Prefix: | mkl_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Amount, before tax, of accumulated other comprehensive income (loss) (AOCI) from (increase) decrease in expected future policy benefit component of liability for future policy benefit from change in discount rate. + References Reference 1: http://www.xbrl.org/2003/role/exampleRef -Topic 944 -SubTopic 40 -Name Accounting Standards Codification -Section 55 -Paragraph 29E -Publisher FASB -URI https://asc.fasb.org//1943274/2147480046/944-40-55-29E Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 944 -SubTopic 40 -Name Accounting Standards Codification -Section 65 -Paragraph 2 -Subparagraph (g)(1) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480016/944-40-65-2 Reference 3: http://www.xbrl.org/2003/role/exampleRef -Topic 944 -SubTopic 40 -Name Accounting Standards Codification -Section 55 -Paragraph 13I -Subparagraph (h) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480046/944-40-55-13I Reference 4: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 944 -SubTopic 40 -Name Accounting Standards Codification -Section 50 -Paragraph 6 -Subparagraph (a) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480081/944-40-50-6 + Details
Name: | us-gaap_AociLiabilityForFuturePolicyBenefitExpectedFuturePolicyBenefitBeforeTax
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Amount, before effect of reinsurance and after current period update of cash flow assumption, of expected future benefit and expense component for liability for future policy benefit, discounted at original rate. + References Reference 1: http://www.xbrl.org/2003/role/exampleRef -Topic 944 -SubTopic 40 -Name Accounting Standards Codification -Section 55 -Paragraph 29E -Publisher FASB -URI https://asc.fasb.org//1943274/2147480046/944-40-55-29E Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 944 -SubTopic 40 -Name Accounting Standards Codification -Section 65 -Paragraph 2 -Subparagraph (g)(1) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480016/944-40-65-2 Reference 3: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 944 -SubTopic 40 -Name Accounting Standards Codification -Section 50 -Paragraph 6 -Subparagraph (a) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480081/944-40-50-6 + Details
Name: | us-gaap_LiabilityForFuturePolicyBenefitExpectedFutureBenefitOriginalDiscountRateBeforeReinsuranceAfterCashFlowChange
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Amount, before effect of reinsurance and after current period update of cash flow assumption and discount rate change, of expected future policy benefit and expense component of liability for future policy benefit. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 944 -SubTopic 40 -Name Accounting Standards Codification -Section 65 -Paragraph 2 -Subparagraph (g)(1) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480016/944-40-65-2 Reference 2: http://www.xbrl.org/2003/role/exampleRef -Topic 944 -SubTopic 40 -Name Accounting Standards Codification -Section 55 -Paragraph 29E -Publisher FASB -URI https://asc.fasb.org//1943274/2147480046/944-40-55-29E Reference 3: http://www.xbrl.org/2003/role/disclosureRef -Topic 944 -SubTopic 40 -Name Accounting Standards Codification -Section 50 -Paragraph 6 -Subparagraph (a) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480081/944-40-50-6 Reference 4: http://www.xbrl.org/2003/role/disclosureRef -Topic 944 -SubTopic 40 -Name Accounting Standards Codification -Section 50 -Paragraph 6 -Subparagraph (b)(1) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480081/944-40-50-6 + Details
Name: | us-gaap_LiabilityForFuturePolicyBenefitExpectedFuturePolicyBenefitBeforeReinsuranceAfterDiscountRateChange
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Amount of cumulative increase (decrease) in expected future policy benefit and expense component for liability of future policy benefit from cash flow assumption change for future cash flows. + References Reference 1: http://www.xbrl.org/2003/role/exampleRef -Topic 944 -SubTopic 40 -Name Accounting Standards Codification -Section 55 -Paragraph 29E -Publisher FASB -URI https://asc.fasb.org//1943274/2147480046/944-40-55-29E Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 944 -SubTopic 40 -Name Accounting Standards Codification -Section 65 -Paragraph 2 -Subparagraph (g)(1) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480016/944-40-65-2 Reference 3: http://www.xbrl.org/2003/role/exampleRef -Topic 944 -SubTopic 40 -Name Accounting Standards Codification -Section 55 -Paragraph 13I -Subparagraph (g) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480046/944-40-55-13I Reference 4: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 944 -SubTopic 40 -Name Accounting Standards Codification -Section 50 -Paragraph 6 -Subparagraph (a) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480081/944-40-50-6 + Details
Name: | us-gaap_LiabilityForFuturePolicyBenefitExpectedFuturePolicyBenefitCumulativeIncreaseDecreaseFromCashFlowChange
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Amount of cumulative increase (decrease) in expected future policy benefit and expense component for liability of future policy benefit from effect of variance from cash flow assumption change for actual experience. + References Reference 1: http://www.xbrl.org/2003/role/exampleRef -Topic 944 -SubTopic 40 -Name Accounting Standards Codification -Section 55 -Paragraph 29E -Publisher FASB -URI https://asc.fasb.org//1943274/2147480046/944-40-55-29E Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 944 -SubTopic 40 -Name Accounting Standards Codification -Section 65 -Paragraph 2 -Subparagraph (g)(1) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480016/944-40-65-2 Reference 3: http://www.xbrl.org/2003/role/exampleRef -Topic 944 -SubTopic 40 -Name Accounting Standards Codification -Section 55 -Paragraph 13I -Subparagraph (f) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480046/944-40-55-13I Reference 4: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 944 -SubTopic 40 -Name Accounting Standards Codification -Section 50 -Paragraph 6 -Subparagraph (a) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480081/944-40-50-6 Reference 5: http://www.xbrl.org/2003/role/disclosureRef -Topic 944 -SubTopic 40 -Name Accounting Standards Codification -Section 50 -Paragraph 6 -Subparagraph (b)(2) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480081/944-40-50-6 + Details
Name: | us-gaap_LiabilityForFuturePolicyBenefitExpectedFuturePolicyBenefitCumulativeIncreaseDecreaseOfActualVarianceFromExpectedExperience
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Amount of interest expense for expected future policy benefit and expense component of liability for future policy benefit. + References Reference 1: http://www.xbrl.org/2003/role/exampleRef -Topic 944 -SubTopic 40 -Name Accounting Standards Codification -Section 55 -Paragraph 29E -Publisher FASB -URI https://asc.fasb.org//1943274/2147480046/944-40-55-29E Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 944 -SubTopic 40 -Name Accounting Standards Codification -Section 65 -Paragraph 2 -Subparagraph (g)(1) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480016/944-40-65-2 Reference 3: http://www.xbrl.org/2003/role/exampleRef -Topic 944 -SubTopic 40 -Name Accounting Standards Codification -Section 55 -Paragraph 13I -Subparagraph (b) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480046/944-40-55-13I Reference 4: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 944 -SubTopic 40 -Name Accounting Standards Codification -Section 50 -Paragraph 6 -Subparagraph (a) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480081/944-40-50-6 + Details
Name: | us-gaap_LiabilityForFuturePolicyBenefitExpectedFuturePolicyBenefitInterestExpense
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Amount, before effect of reinsurance and current period update of cash flow assumption, of expected future policy benefit and expense component of liability for future policy benefit, discounted at original rate. + References Reference 1: http://www.xbrl.org/2003/role/exampleRef -Topic 944 -SubTopic 40 -Name Accounting Standards Codification -Section 55 -Paragraph 29E -Publisher FASB -URI https://asc.fasb.org//1943274/2147480046/944-40-55-29E Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 944 -SubTopic 40 -Name Accounting Standards Codification -Section 65 -Paragraph 2 -Subparagraph (g)(1) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480016/944-40-65-2 Reference 3: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 944 -SubTopic 40 -Name Accounting Standards Codification -Section 50 -Paragraph 6 -Subparagraph (a) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480081/944-40-50-6 + Details
Name: | us-gaap_LiabilityForFuturePolicyBenefitExpectedFuturePolicyBenefitOriginalDiscountRateBeforeCashFlowAndReinsurance
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Amount, before effect of reinsurance, of undiscounted balance for expected future policy benefit and expense component of liability for future policy benefit. + References Reference 1: http://www.xbrl.org/2003/role/exampleRef -Topic 944 -SubTopic 40 -Name Accounting Standards Codification -Section 55 -Paragraph 29E -Publisher FASB -URI https://asc.fasb.org//1943274/2147480046/944-40-55-29E Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Topic 944 -SubTopic 40 -Name Accounting Standards Codification -Section 50 -Paragraph 6 -Subparagraph (b)(1) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480081/944-40-50-6 + Details
Name: | us-gaap_LiabilityForFuturePolicyBenefitExpectedFuturePolicyBenefitUndiscountedBeforeReinsurance
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- References No definition available. + Details
Name: | us-gaap_LiabilityForFuturePolicyBenefitsActivityAbstract
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Amount of cash outflow to policyholder from benefit payment for expected future policy benefit and expense component of liability for future policy benefit. + References Reference 1: http://www.xbrl.org/2003/role/exampleRef -Topic 944 -SubTopic 40 -Name Accounting Standards Codification -Section 55 -Paragraph 29E -Publisher FASB -URI https://asc.fasb.org//1943274/2147480046/944-40-55-29E Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 944 -SubTopic 40 -Name Accounting Standards Codification -Section 65 -Paragraph 2 -Subparagraph (g)(1) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480016/944-40-65-2 Reference 3: http://www.xbrl.org/2003/role/exampleRef -Topic 944 -SubTopic 40 -Name Accounting Standards Codification -Section 55 -Paragraph 13I -Subparagraph (d) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480046/944-40-55-13I Reference 4: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 230 -SubTopic 10 -Name Accounting Standards Codification -Section 45 -Paragraph 17 -Subparagraph (f) -Publisher FASB -URI https://asc.fasb.org//1943274/2147482740/230-10-45-17 Reference 5: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 944 -SubTopic 40 -Name Accounting Standards Codification -Section 50 -Paragraph 6 -Subparagraph (a) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480081/944-40-50-6 + Details
Name: | us-gaap_LiabilityForFuturePolicyBenefitsPaymentForBenefits
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration