The increase (decrease) during the reporting period in obligations evidenced by formal promissory notes.

No definition available.

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Namespace Prefix:	brka_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Face (par) amount of debt instrument at time of issuance.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 55
-Paragraph 8
-URI http://asc.fasb.org/extlink&oid=64930739&loc=d3e28878-108400

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=64930785&loc=d3e28551-108399

+ Details

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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://www.xbrl.org/2003/role/presentationRef
-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=6877327&loc=d3e13212-122682

+ Details

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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

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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/presentationRef
-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

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 830
-SubTopic 20
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=64836518&loc=d3e30700-110894

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 830
-SubTopic 20
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=64836518&loc=d3e30690-110894

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- 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

No definition available.

+ Details

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

Notes payable and other borrowings - Narrative (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Jan. 31, 2018
Insurance and Other [Member] \| Subsidiaries [Member]
Debt Instrument [Line Items]
Weighted average interest rate, percentage	4.00%
Insurance and Other [Member] \| Euro Denominated [Member] \| Berkshire Hathaway Inc. (Parent) [Member]
Debt Instrument [Line Items]
Weighted average interest rate, percentage	1.10%
Insurance and Other [Member] \| Euro Denominated [Member] \| Senior Notes [Member] \| Berkshire Hathaway Inc. (Parent) [Member]
Debt Instrument [Line Items]
Increase in carrying value of notes	$ 217
Insurance and Other [Member] \| Euro Denominated [Member] \| Senior Notes [Member] \| Interest Expense [Member] \| Berkshire Hathaway Inc. (Parent) [Member]
Debt Instrument [Line Items]
Revaluation attributable to changes in foreign currency exchange rates	217
Insurance and Other [Member] \| U.S. Dollar Denominated [Member] \| Berkshire Hathaway Inc. (Parent) [Member]
Debt Instrument [Line Items]
Repayments of borrowings	$ 800
Weighted average interest rate, percentage	3.00%
Berkshire Hathaway Energy Company and Subsidiaries [Member] \| Railroad, Utilities and Energy [Member] \| Debt Due 2021 to 2048 [Member] \| Senior Notes [Member] \| Subsidiaries [Member]
Debt Instrument [Line Items]
Principal amount of debt issued		$ 2,200
Weighted average interest rate, percentage		3.20%
BNSF [Member] \| Railroad, Utilities and Energy [Member] \| Subsidiaries [Member]
Debt Instrument [Line Items]
Repayments of borrowings	$ 650
Weighted average interest rate, percentage	4.70%
BNSF [Member] \| Railroad, Utilities and Energy [Member] \| Debentures Due 2048 at 4.05% [Member] \| Senior Unsecured Debentures [Member] \| Subsidiaries [Member]
Debt Instrument [Line Items]
Principal amount of debt issued	$ 750
Debt instrument, interest rate, stated percentage	4.05%
Berkshire Hathaway Finance Corporation [Member] \| Finance and Financial Products [Member] \| Subsidiaries [Member]
Debt Instrument [Line Items]
Weighted average interest rate, percentage	3.10%
Berkshire Hathaway Finance Corporation [Member] \| Finance and Financial Products [Member] \| Senior Notes [Member] \| Subsidiaries [Member]
Debt Instrument [Line Items]
Repayments of borrowings	$ 2,350