Reinsurance - Variable Annuity Reinsurance Agreement (Details) - Variable Annuity - Berkshire Hathway Life Insurance Company Of Nebraska - USD ($) $ in Billions	9 Months Ended	12 Months Ended
Sep. 30, 2025	Dec. 31, 2013
Ceded Credit Risk [Line Items]
Reinsurance, Reinsured Risk, Percentage		100.00%
Remaining overall limit under reinsurance agreement	$ 3.0
Secured \| Market risk benefits reinsurance recoverable, including IBNR and outstanding claims, less premiums due \| Collateralization risk
Ceded Credit Risk [Line Items]
Concentration percentage	100.00%

Amount remaining of overall limit to claims covered under ceded reinsurance agreement.

No definition available.

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- 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

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 944
-SubTopic 825
-Name Accounting Standards Codification
-Section 50
-Paragraph 1B
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147477351/944-825-50-1B

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
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- Definition

For an entity that discloses a concentration risk in relation to quantitative amount, which serves as the "benchmark" (or denominator) in the equation, this concept represents the concentration percentage derived from the division.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 42
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482810/280-10-50-42

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 275
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-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482861/275-10-50-18

Reference 3: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 275
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-URI https://asc.fasb.org/1943274/2147482861/275-10-50-18

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
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- Definition

Percentage of risk undertaken originally by insurer ceded to reinsurer.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
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-SubTopic 20
-Name Accounting Standards Codification
-Section 50
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-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479838/944-20-50-3

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- Details

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