75000 - Document - Document and Entity Information link:presentationLink link:calculationLink link:definitionLink 75010 - Statement - Statements of Net Assets Available for Benefits link:presentationLink link:calculationLink link:definitionLink 75020 - Statement - Statement of Changes in Net Assets Available for Benefits link:presentationLink link:calculationLink link:definitionLink 75030 - Disclosure - Description of The Plan link:presentationLink link:calculationLink link:definitionLink 75040 - Disclosure - Summary of Significant Accounting Policies link:presentationLink link:calculationLink link:definitionLink 75050 - Disclosure - Fair Value Measurements link:presentationLink link:calculationLink link:definitionLink 75060 - Disclosure - Plan Termination link:presentationLink link:calculationLink link:definitionLink 75070 - Disclosure - Related Party And Party-in-interest Transactions link:presentationLink link:calculationLink link:definitionLink 75080 - Disclosure - Federal Income Tax Status link:presentationLink link:calculationLink link:definitionLink 75090 - Disclosure - Subsequent Events link:presentationLink link:calculationLink link:definitionLink 75100 - Disclosure - Schedule of Assets (Held at End of Year) link:presentationLink link:calculationLink link:definitionLink 75110 - Disclosure - Summary of Significant Accounting Policies (Policies) link:presentationLink link:calculationLink link:definitionLink 75120 - Disclosure - Fair Value Measurements (Tables) link:presentationLink link:calculationLink link:definitionLink 75130 - Disclosure - Schedule of Assets (Held at End of Year) (Tables) link:presentationLink link:calculationLink link:definitionLink 75140 - Disclosure - Description of The plan - Additional Information (Details) link:presentationLink link:calculationLink link:definitionLink 75150 - Disclosure - Fair Value Measurements - Schedule of Net Asset Value Investments are Included to Permit Reconciliation to the Statement of Net Assets Available for Benefits (Details) link:presentationLink link:calculationLink link:definitionLink 75160 - Disclosure - Related Party And Party-in-interest Transactions - Additional Information (Details) link:presentationLink link:calculationLink link:definitionLink 75170 - Disclosure - Federal Income Tax Status - Additional Information (Details) link:presentationLink link:calculationLink link:definitionLink 75180 - Disclosure - Schedule of Assets (Held at End of Year) - Schedule of Assets (Details) link:presentationLink link:calculationLink link:definitionLink 75180 - Disclosure - Schedule of Assets (Held at End of Year) - Schedule of Assets (Details) [Default] link:presentationLink link:calculationLink link:definitionLink EBP, Change in Net Asset Available for Benefit, Decrease from Payment to Participant Benefits paid to participants EBP, Employer, Common Stock, Class B [Member] Berkshire Common Stock EBP, Receivable [Abstract] Receivables: Berkshire B Unitized Stock Fund Money Market [Member] Berkshire B Unitized Stock Fund Money Market. Berkshire B Unitized Stock Fund - Money Market Fair Value, Inputs, Level 2 [Member] Other Observable Inputs (Level 2) EBP, Related Party and Party-in-Interest Transactions [Line Items] Document Fiscal Period Focus EBP, Tax Status [Abstract] Berkshire B Unitized Stock Fund Stock [Member] Berkshire B Unitized Stock Fund Stock. Berkshire B Unitized Stock Fund - Stock Employee benefit plan, forfeited non-vested EBP, Forfeited Nonvested Account EBP, Description of Plan [Text Block] Description of The Plan Investment, Identifier [Axis] EBP, Description of Plan [Line Items] Employee Benefit Plan Forfeited Allocated to Participant Accounts Employee benefit plan forfeited allocated to participant accounts. Employee benefit plan forfeited allocated to participant accounts Berkshire B Unitized Stock Fund Berkshire B Unitized Stock Fund [Member] Berkshire B Unitized Stock Fund. Interest rate EBP, Debt, Interest Rate Participant Directed Berkshire B ESOP [Member] Participant directed Berkshire B ESOP. Participant Directed Berkshire B ESOP EBP, Employer Contribution, Matching Percentage EBP, Investment, Issuer Name [Extensible Enumeration] EBP, Investment, Fair Value and NAV [Abstract] Employee benefit plan subsequent event. Employee Benefit Plan Subsequent Event [Table] EBP, Accounting Policy [Line Items] EBP, Change in Net Asset Available for Benefit, Transfer to (from) Plan Interfund transfers EBP, Schedule of Asset Held for Investment [Table] EBP, Statement of Net Asset Available for Benefit [Line Items] EBP, Contribution [Table] Employee Benefit Plan Conversion Of Preferred Stock Employee benefit plan conversion of preferred stock. Employee benefit plan conversion of preferred stock EBP, Note Receivable from Participant, Account, Maximum Borrowing, Amount Employee benefit plan, vested account balance Preferred Stock [Member] Preferred Stock Aviation Underwriters, Inc [Member] Aviation Underwriters, Inc. Aviation Underwriters, Inc Collective Trust Fund Common Collective Trust [Member] Amendment Flag EBP, Change in Net Asset Available for Benefit, Increase from Employer Contribution, Cash and Noncash EBP, Change in Net Asset Available for Benefit, Increase from Employer Contribution, Cash and Noncash, Total Employer contributions - cash match/discretionary contribution EBP, Change in Net Asset Available for Benefit, Decrease [Abstract] DEDUCTIONS EBP, Payment to Participant [Policy Text Block] Benefit Paid to Participants Payment of Benefits Employee Benefit Plan Participant Contribution automatically enrolled pre tax deferral rate Employee benefit plan participant contribution automatically enrolled pre tax deferral rate. Automatically enrolled pre-tax deferral rate EBP, Schedule of Asset Held for Investment [Line Items] Fair Value Hierarchy and NAV [Axis] EBP, Investment, Current Value, Type [Extensible Enumeration] Investment Type [Axis] Document Type EBP, Participant-Directed [Member] Participant Directed Investments Entity Central Index Key EBP, Investment [Policy Text Block] Investment Valuation and Income Recognition EBP, Accounting Policy [Table] EBP, Basis of Accounting [Policy Text Block] Basis of Accounting EBP, Description of Plan [Table] EBP, Participant-Directed and Nonparticipant-Directed Status [Axis] Employee Benefit Plan Tranche Two [Member] Employee Benefit Plan tranche two. Two years EBP, Investment, Fair Value [Abstract] Investments - at fair value: Number of shares held in plan EBP, Investment, Number of Shares Minimum [Member] Minimum EBP, Related Party and Party-in-Interest Transactions [Text Block] Related Party And Party-in-Interest Transactions EBP, Change in Net Asset Available for Benefit, Increase Total additions Fair Value, Inputs, Level 3 [Member] Significant Unobservable Inputs (Level 3) EBP, Change in Net Asset Available for Benefit, Increase from Contribution Total contributions EBP, Asset Held for Investment, Investment, Excluding Plan Interest in Master Trust, Participation Status [Extensible Enumeration] Employee benefit plan debt repaid year. Debt repaid year Employee Benefit Plan Tranche Three [Member] Employee benefit plan tranche three. Three years Service fees EBP, Expense [Policy Text Block] Scenario [Axis] Document Information [Line Items] Other EBP, Other Investment [Member] Fair Value Measured at Net Asset Value Per Share [Member] Net Asset Value Per Share EBP, Statement of Net Asset Available for Benefit [Abstract] Fair Value Hierarchy Fair Value, Inputs, Level 1, Level 2, and Level 3 [Member] EBP, Change in Net Asset Available for Benefit, Increase from Contribution [Abstract] Contributions: EBP, Tax Determination Letter, Date Tax determination letter, date EBP, Related Party and Party-in-Interest Transactions [Abstract] EBP, Investment, Excluding Plan Interest in Master Trust, Fair Value EBP, Investment, Excluding Plan Interest in Master Trust, Fair Value, Ending Balance EBP, Investment, Excluding Plan Interest in Master Trust, Fair Value, Beginning Balance EBP, Investment, Excluding Plan Interest in Master Trust, Fair Value, Total Total investments Fair value of investments Employee benefit plan employer discretionary contributions amount. Discretionary contributions amount EBP, Use of Estimate [Policy Text Block] Use of Estimates Debt Instrument, Name [Domain] Mutual Fund [Member] Mutual Funds Entity [Domain] Employee Benefit Plan Subsequent Events [Abstract] Employee benefit plan subsequent events. EBP, Summary of Accounting Policy [Text Block] Summary of Significant Accounting Policies EBP, Investment, Fair Value and NAV [Text Block] Fair Value Measurements EBP, Description of Plan and Accounting Change [Abstract] EBP, Asset Held for Investment, Participant Loan, after Deemed Distribution Notes receivable from participants EBP, Statement of Change in Net Asset Available for Benefit [Line Items] Statistical Measurement [Domain] EBP, Note Receivable from Participant Notes receivable from participants Document Period End Date Fair Value Hierarchy and NAV [Domain] Employee Benefit Plan Debt Maturity Year Employee benefit plan debt maturity year. Debt repayment year EBP, Risk and Uncertainty [Policy Text Block] Risks and Uncertainties Berkshire B ESOP Fund [Member] Berkshire B ESOP Fund. Berkshire B ESOP Fund EBP, Contribution [Abstract] EBP, Tax Determination Letter, Obtained [true false] Tax determination letter, obtained EBP, Related Party and Party-in-Interest Transactions [Table] EBP, Plan Termination [Text Block] Plan Termination EBP, Subsequent Event [Text Block] Subsequent Events EBP, Change in Net Asset Available for Benefit, Increase from Interest Income on Investment Interest income on notes receivable from participants EBP, Participant-Directed and Nonparticipant-Directed Status [Domain] Contribution for tax deferred subject to IRC Limitations EBP, Participant Contribution, Pretax, Maximum Annual Compensation, Amount Cover [Abstract] Investments [Domain] Scenario [Domain] Term loan EBP, Debt EBP, Debt, Total EBP, Net Asset Available for Benefit Beginning of year End of year NET ASSETS AVAILABLE FOR BENEFITS EBP, Investment, Fair Value and NAV [Table Text Block] Schedule of Net Asset Value Investments are Included to Permit Reconciliation to the Statement of Net Assets Available for Benefits Employee Benefit Plan Asset Liability For Uncertain Tax Positions Amount recognized for uncertainty in income taxes positions taken or expected to be taken classified as an asset (liability) for employee stock purchase, saving, or similar plan (employee benefit plan (EBP)). (Asset) liability for uncertain tax positions Employee benefit plan participant contribution discretionary contribution percentage. Discretionary contribution percentage Employee Benefit Plan Tranche Four [Member] Employee benefit plan tranche four. Four years EBP, Contribution [Line Items] EBP, Net Asset Available for Benefit [Abstract] NET ASSETS AVAILABLE FOR BENEFITS: EBP, Schedule of Asset Held for Investment [Abstract] Convertible Preferred Stock [Member] 7-1/4% Cumulative Convertible Preferred Stock Employee benefit plan participant maximum annual catch up contribution amount Employee benefit plan participant maximum annual catch up contribution amount. Purchase of Shares Berkshire B ESOP Fund Stock [Member] Berkshire B ESOP Fund Stock. Berkshire B ESOP Fund - Stock EBP, Asset Held for Investment, Investment, Excluding Plan Interest in Master Trust, Current Value Current Value EBP, Note Receivable from Participant [Policy Text Block] Notes Receivable from Participants EBP, Schedule of Asset Held for Investment [Table Text Block] Schedule of Assets EBP, Investment, Purchased, Number of Shares Purchase of shares EBP, Statement of Net Asset Available for Benefit [Table] Document Fiscal Year Focus Net appreciation in fair value of investments EBP, Change in Net Asset Available for Benefit, Increase (Decrease) from Gain (Loss) on Investment EBP, Change in Net Asset Available for Benefit, Increase (Decrease) from Gain (Loss) on Investment, Total Fund appreciated by assets Employee Benefit Plan Employer Contribution Vested Percentage Employee benefit plan employer contribution vested percentage. Vested Percentage Employee Benefit Plan Preferred Stock Conversion Converted into Common Stock Employee benefit plan preferred stock conversion converted into common stock. EBP, Employer Contribution, Participant Compensation Matched, Percentage Percentage on employee eligible compensation EBP, Statement of Change in Net Asset Available for Benefit [Table] Employee Benefit Plan Note Receivable From Participant Interest Rate Employee benefit plan note receivable from participant interest rate. Employee benefit plan note receivable from participant interest rate Amended Loan [Member] Amended loan. Amended Loan Employee Benefit Plan Change in Net Asset Available for Benefit Increase (Decrease) from Stock Investment Portion Employee benefit plan change in net asset available for benefit increase (decrease) from stock investment portion. Stock investment portion Debt Instrument [Axis] Employee Benefit Plan Vesting [Axis] Employee benefit plan vesting [Axis] Employee benefit plan participant contribution automatic increased rate Employee Benefit Plan Participant Contribution Automatic Increased Rate Employee benefit plan participant contribution automatic increased rate. EBP, Participant Contribution, Pretax, Maximum Annual Compensation to Total Compensation, Percentage Participants contribute percentage EBP, Plan Number Employee benefit plan employer contribution matching amount Employee Benefit Plan Employer Contribution Matching Amount Employee benefit plan employer contribution matching amount. EBP, Investment, Fair Value and NAV [Line Items] Document Information [Table] Legal Entity [Axis] EBP, Plan Name EBP, Asset [Abstract] ASSETS EBP, Investment, Fair Value and NAV [Table] Employee Benefit Plan Vesting [Domain] Employee benefit plan vesting. EBP, Accounting Policy, Accounting Standard Update, and Change in Accounting Principle [Abstract] EBP, Asset Held for Investment EBP, Asset Held for Investment, Total Total assets held for investment purposes EBP, Tax Status [Text Block] Federal Income Tax Status EBP, Investment, Sold, Number of Shares Number of common stock sold Maximum [Member] Maximum Statistical Measurement [Axis] EBP, Statement of Change in Net Asset Available for Benefit [Abstract] Number of Common stock transferred out of Plan Employee benefit plan number of common stock transferred out of Plan. Dividends EBP, Change in Net Asset Available for Benefit, Increase from Dividend Income on Investment Entity Registrant Name Employee benefit plan forfeited Employee benefit plan forfeited. Participant Directed Other [Member] Participant directed other. Participant Directed Other EBP, Receivable Total receivables EBP 002 [Member] EBP 002. EBP 002 EBP, Asset Held for Investment, Participant Loan, Interest Rate Schedule of Assets (Held at End of Year) Employee Benefit Plan Schedule of Assets Held at End of Year [TextBlock] Employee benefit plan schedule of assets held at end of year. Employee benefit plan, asset held for investment, participant loan, maturity year Employee Benefit Plan Participant Loan Maturity Year Employee benefit plan participant loan maturity year. Employee Benefit Plan Participant Maximum Annual Compensation Percentage Employee benefit plan participant maximum annual compensation percentage. Employee benefit plan participant maximum annual compensation percentage Employee benefit Plan non participating eligible employees contribution rate Employee benefit plan non participating eligible employees contribution rate. Berkshire B Unitized Fund [Member] Berkshire B Unitized Fund. Berkshire B Unitized Fund Employee Benefit Plan Service fees revenue credits net Employee benefit plan service fees revenue credits net. Service fees (revenue credits), net EBP, Change in Net Asset Available for Benefit, Decrease Total deductions Employee Benefit Plan Note Receivable From Participant Repayment Term Employee benefit plan note receivable from participant repayment term. Employee benefit plan note receivable from participant repayment term Fair Value, Inputs, Level 1 [Member] Active Markets for Identical Assets (Level 1) Term loan. Term Loan [Member] Term Debt [Member] Term Loan Employee Benefit Plan Immediate Lump Sum Distributions Transferred to Individual Retirement Account Employee benefit plan immediate lump sum distributions transferred to individual retirement account. Employee benefit plan immediate lump sum distributions transferred to individual retirement account EBP, Change in Net Asset Available for Benefit, Increase from Participant Contribution EBP, Change in Net Asset Available for Benefit, Increase from Participant Contribution, Total Participant contributions Employee benefit plan subsequent event line items. Employee Benefit Plan Subsequent Event [Line Items] EBP, Tax Status [Line Items] Employee benefits plan participants contribution to increase the percentage rate automatically. Employee benefits plan participants contribution to increase the percentage rate automatically Entity Tax Identification Number Employee Benefit Plan Catch-Up Contributions Eligible Age Employee benefit plan catch-up contributions eligible age. Catch-Up contributions eligible age EBP, Change in Net Asset Available for Benefit, Increase (Decrease) Increase in Net Assets Increase in Net Assets EBP, Tax Status [Table] Employee Benefit Plan Stock Split Conversion Ratio Employee benefit plan stock split conversion ratio. Common stock split EBP, Asset Held for Investment, Party-in-Interest [true false] Berkshire Hathaway [Member] Vanguard BlackRock member. American Funds [Member] PIMCO [Member] BlackRock [Member] Fidelity Management Trust Co [Member] PIMCO member. Berkshire Hathaway member. American Beacon [Member] American funds member. Fidelity [Member] Fidelity member. American beacon member. Fidelity management trust co member. Neuberger Berman [Member] Neuberger Berman member. Vanguard [Member]