Percent of manufactured housing loan balances evaluated collectively for impairment.

No definition available.

Name:	brka_PercentOfLoanBalancesEvaluatedCollectivelyForImpairment
Namespace Prefix:	brka_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Percent of loan balances that are current as to payment status.

+ References

No definition available.

+ Details

Name:	brka_PercentOfLoanBalancesWithPaymentStatusCurrent
Namespace Prefix:	brka_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- 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_AccountsNotesAndLoansReceivableLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Date the credit facility terminates, in CCYY-MM-DD format.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.19(b),22(b))
-URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682

+ Details

Name:	us-gaap_LineOfCreditFacilityExpirationDate1
Namespace Prefix:	us-gaap_
Data Type:	xbrli:dateItemType
Balance Type:	na
Period Type:	duration

- Definition

Maximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility.

+ References

+ Details

Name:	us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount before allowance of loans and leases held in portfolio, including but not limited to, commercial and consumer loans. Includes deferred interest and fees, undisbursed portion of loan balance, unamortized costs and premiums and discounts from face amounts. Excludes loans and leases covered under loss sharing agreements.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=121593590&loc=d3e4428-111522

+ Details

Name:	us-gaap_LoansAndLeasesReceivableGrossCarryingAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Details

Name:	srt_CounterpartyNameAxis=brka_SeritageGrowthPropertiesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_CreditFacilityAxis=brka_TermLoanMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_CounterpartyNameAxis=brka_LeeEnterprisesIncMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis=us-gaap_LoansAndFinanceReceivablesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis=brka_ManufacturedHousingLoanBalanceMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Loans and finance receivables - Narrative (Detail) - USD ($)	6 Months Ended
	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019
Seritage Growth Properties [Member] \| Term Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loan facility amount	$ 2,000,000,000.0
Expiration date of term loan	Jul. 31, 2023
Outstanding loan balance	$ 1,600,000,000		$ 1,600,000,000
Lee Enterprises, Inc. [Member] \| Term Loan [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Term loan facility amount		$ 576,000,000
Loans and Finance Receivables [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Percent of manufactured housing loan balances evaluated collectively for impairment	99.00%
Manufactured Housing Loan Balances [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Percent of loan balances considered to be current as to payment status	98.00%