Year the debt matures, in CCYY format.

No definition available.

Name:	brka_DebtInstrumentMaturityYear
Namespace Prefix:	brka_
Data Type:	xbrli:gYearItemType
Balance Type:	na
Period Type:	duration

- Definition

The principal amount of new debt issued during the period, excluding premium or discount, if any.

+ References

No definition available.

+ Details

Name:	brka_DebtIssuedDuringPeriod
Namespace Prefix:	brka_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Amount of long-term debt due after one year or the normal operating cycle, if longer, assumed at the acquisition date.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=121647850&loc=d3e4845-128472

+ Details

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

- Definition

Amount of short-term and long-term debt and lease obligation.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03.13,16)
-URI http://asc.fasb.org/extlink&oid=120398452&loc=d3e534808-122878

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03.16)
-URI http://asc.fasb.org/extlink&oid=120400017&loc=d3e572229-122910

+ Details

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

- Definition

Contractual interest rate for funds borrowed, under the debt agreement.

+ 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 210.5-02.22(a)(1))
-URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682

+ Details

Name:	us-gaap_DebtInstrumentInterestRateStatedPercentage
Namespace Prefix:	us-gaap_
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_DebtInstrumentLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Weighted average interest rate of debt outstanding.

+ References

No definition available.

+ Details

Name:	us-gaap_DebtWeightedAverageInterestRate
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Amount before tax of foreign currency transaction realized and unrealized gain (loss) recognized in the income statement.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 830
-SubTopic 20
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=109240200&loc=d3e30690-110894

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 830
-SubTopic 20
-Section 35
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=121605123&loc=d3e30226-110892

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 830
-SubTopic 10
-Section 45
-Paragraph 17
-URI http://asc.fasb.org/extlink&oid=120253306&loc=d3e28228-110885

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 830
-SubTopic 20
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=6450222&loc=d3e30840-110895

+ Details

Name:	us-gaap_ForeignCurrencyTransactionGainLossBeforeTax
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Maximum potential amount of future payments (undiscounted) the guarantor could be required to make under the guarantee or each group of similar guarantees before reduction for potential recoveries under recourse or collateralization provisions.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 460
-SubTopic 10
-Section 50
-Paragraph 4
-Subparagraph (b)(1)
-URI http://asc.fasb.org/extlink&oid=121555522&loc=d3e12069-110248

+ Details

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

- Definition

The cash outflow during the period from the repayment of aggregate short-term and long-term debt. Excludes payment of capital lease obligations.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 15
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=121586364&loc=d3e3291-108585

+ Details

Name:	us-gaap_RepaymentsOfDebt
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

Notes payable and other borrowings - Narrative (Detail) € in Millions, £ in Millions, $ in Millions, ¥ in Billions	1 Months Ended			12 Months Ended
	Apr. 30, 2020 USD ($)	Apr. 30, 2020 JPY (¥)	Mar. 31, 2020 EUR (€)	Dec. 31, 2020 USD ($)	Dec. 31, 2020 EUR (€)	Dec. 31, 2020 JPY (¥)	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2020 EUR (€)	Dec. 31, 2020 JPY (¥)	Dec. 31, 2020 GBP (£)	Nov. 01, 2020 USD ($)
Debt Instrument [Line Items]
Notes payable and other borrowings									€ 6,850	¥ 625.5	£ 1,750
Berkshire Hathaway Inc. (Parent) [Member]
Debt Instrument [Line Items]
Repayments of borrowings				$ 1,151			$ 758	$ 1,563
Gain (loss) attributable to changes in foreign currency exchange rates				(970)			193	366
Notes payable and other borrowings				22,665			19,903
Subsidiaries [Member] \| Berkshire Hathaway Energy and Subsidiaries [Member] \| Dominion Pipeline Business [Member]
Debt Instrument [Line Items]
Business acquisition assumed debt												$ 5,600
Insurance and Other [Member]
Debt Instrument [Line Items]
Notes payable and other borrowings				41,522			37,590
Insurance and Other [Member] \| Berkshire Hathaway Inc. (Parent) [Member] \| Subsidiaries Excluding Berkshire Hathaway Finance Corporation [Member]
Debt Instrument [Line Items]
Guarantee obligation				$ 1,200
Insurance and Other [Member] \| Subsidiaries [Member]
Debt Instrument [Line Items]
Weighted average interest rate, percentage				4.20%					4.20%	4.20%	4.20%
Insurance and Other [Member] \| Subsidiaries [Member] \| Minimum [Member]
Debt Instrument [Line Items]
Debt maturity year				2021	2021	2021
Insurance and Other [Member] \| Subsidiaries [Member] \| Maximum [Member]
Debt Instrument [Line Items]
Debt maturity year				2045	2045	2045
Insurance and Other [Member] \| Senior Notes [Member] \| Berkshire Hathaway Inc. (Parent) [Member]
Debt Instrument [Line Items]
Gain (loss) attributable to changes in foreign currency exchange rates				$ (1,000)			192	$ 366
Insurance and Other [Member] \| Senior Notes [Member] \| Subsidiaries [Member] \| Berkshire Hathaway Finance Corporation [Member]
Debt Instrument [Line Items]
Repayments of borrowings				900
Principal amount of debt issued				$ 3,000
Insurance and Other [Member] \| Senior Notes [Member] \| Notes Due 2025 at 0.0% [Member] \| Berkshire Hathaway Inc. (Parent) [Member]
Debt Instrument [Line Items]
Repayments of borrowings \| €			€ 1,000		€ 1,000
Principal amount of debt issued \| €			€ 1,000		€ 1,000
Debt instrument, interest rate, stated percentage			0.00%	0.00%					0.00%	0.00%	0.00%
Debt maturity year			2025	2025	2025	2025
Insurance and Other [Member] \| Senior Notes [Member] \| Debt Due 2023 To 2060 [Member] \| Berkshire Hathaway Inc. (Parent) [Member]
Debt Instrument [Line Items]
Principal amount of debt issued	$ 1,800	¥ 195.5		$ 1,800		¥ 195.5
Weighted average interest rate, percentage	1.07%	1.07%		1.07%					1.07%	1.07%	1.07%
Insurance and Other [Member] \| Senior Notes [Member] \| Debt Due 2023 To 2060 [Member] \| Berkshire Hathaway Inc. (Parent) [Member] \| Minimum [Member]
Debt Instrument [Line Items]
Debt maturity year	2023	2023		2023	2023	2023
Insurance and Other [Member] \| Senior Notes [Member] \| Debt Due 2023 To 2060 [Member] \| Berkshire Hathaway Inc. (Parent) [Member] \| Maximum [Member]
Debt Instrument [Line Items]
Debt maturity year	2060	2060		2060	2060	2060
Insurance and Other [Member] \| Senior Notes [Member] \| Notes Due 2030 at 1.45% [Member] \| Subsidiaries [Member] \| Berkshire Hathaway Finance Corporation [Member]
Debt Instrument [Line Items]
Principal amount of debt issued				$ 750
Debt instrument, interest rate, stated percentage				1.45%					1.45%	1.45%	1.45%
Debt maturity year				2030	2030	2030
Insurance and Other [Member] \| Senior Notes [Member] \| Notes Due 2030 at 1.85% [Member] \| Subsidiaries [Member] \| Berkshire Hathaway Finance Corporation [Member]
Debt Instrument [Line Items]
Principal amount of debt issued				$ 500
Debt instrument, interest rate, stated percentage				1.85%					1.85%	1.85%	1.85%
Debt maturity year				2030	2030	2030
Insurance and Other [Member] \| Senior Notes [Member] \| Notes Due 2050 at 2.85% [Member] \| Subsidiaries [Member] \| Berkshire Hathaway Finance Corporation [Member]
Debt Instrument [Line Items]
Principal amount of debt issued				$ 1,750
Debt instrument, interest rate, stated percentage				2.85%					2.85%	2.85%	2.85%
Debt maturity year				2050	2050	2050
Railroad, Utilities and Energy [Member]
Debt Instrument [Line Items]
Notes payable and other borrowings				$ 75,373			$ 65,778
Railroad, Utilities and Energy [Member] \| Subsidiaries [Member] \| Berkshire Hathaway Energy and Subsidiaries [Member]
Debt Instrument [Line Items]
Repayments of borrowings				3,200
Railroad, Utilities and Energy [Member] \| Debt Due 2025 To 2062 [Member] \| Subsidiaries [Member] \| Berkshire Hathaway Energy and Subsidiaries [Member]
Debt Instrument [Line Items]
Principal amount of debt issued				$ 7,600
Weighted average interest rate, percentage				3.20%					3.20%	3.20%	3.20%
Railroad, Utilities and Energy [Member] \| Debt Due 2025 To 2062 [Member] \| Subsidiaries [Member] \| Minimum [Member] \| Berkshire Hathaway Energy and Subsidiaries [Member]
Debt Instrument [Line Items]
Debt maturity year				2025	2025	2025
Railroad, Utilities and Energy [Member] \| Debt Due 2025 To 2062 [Member] \| Subsidiaries [Member] \| Maximum [Member] \| Berkshire Hathaway Energy and Subsidiaries [Member]
Debt Instrument [Line Items]
Debt maturity year				2062	2062	2062
Railroad, Utilities and Energy [Member] \| Senior Unsecured Debenture [Member] \| Debentures Due 2051 [Member] \| Subsidiaries [Member] \| BNSF [Member]
Debt Instrument [Line Items]
Repayments of borrowings				$ 570
Principal amount of debt issued				$ 575
Debt instrument, interest rate, stated percentage				3.05%					3.05%	3.05%	3.05%
Debt maturity year				2051	2051	2051