Notes payable and other borrowings (Detail) - USD ($) $ in Millions	3 Months Ended
Mar. 31, 2018	Dec. 31, 2017
Railroad, Utilities and Energy [Member]
Debt Instrument [Line Items]
Notes payable and other borrowings	$ 62,667	$ 62,178
Railroad, Utilities and Energy [Member] \| Subsidiaries [Member] \| Berkshire Hathaway Energy [Member]
Debt Instrument [Line Items]
Weighted average interest rate, percentage	4.60%
Senior unsecured debt	$ 8,627	6,452
Railroad, Utilities and Energy [Member] \| Subsidiaries [Member] \| Berkshire Hathaway Energy [Member] \| Minimum [Member]
Debt Instrument [Line Items]
Debt maturity year	2018
Railroad, Utilities and Energy [Member] \| Subsidiaries [Member] \| Berkshire Hathaway Energy [Member] \| Maximum [Member]
Debt Instrument [Line Items]
Debt maturity year	2048
Railroad, Utilities and Energy [Member] \| Subsidiaries [Member] \| Berkshire Hathaway Energy Subsidiaries [Member]
Debt Instrument [Line Items]
Short-term debt, weighted average interest rate	2.60%
Weighted average interest rate, percentage	4.80%
Notes payable and other borrowings	$ 28,871	28,739
Short-term debt	$ 2,608	4,488
Railroad, Utilities and Energy [Member] \| Subsidiaries [Member] \| Berkshire Hathaway Energy Subsidiaries [Member] \| Minimum [Member]
Debt Instrument [Line Items]
Debt maturity year	2018
Railroad, Utilities and Energy [Member] \| Subsidiaries [Member] \| Berkshire Hathaway Energy Subsidiaries [Member] \| Maximum [Member]
Debt Instrument [Line Items]
Debt maturity year	2064
Railroad, Utilities and Energy [Member] \| Subsidiaries [Member] \| BNSF [Member]
Debt Instrument [Line Items]
Weighted average interest rate, percentage	4.70%
Notes payable and other borrowings	$ 22,561	22,499
Railroad, Utilities and Energy [Member] \| Subsidiaries [Member] \| BNSF [Member] \| Minimum [Member]
Debt Instrument [Line Items]
Debt maturity year	2018
Railroad, Utilities and Energy [Member] \| Subsidiaries [Member] \| BNSF [Member] \| Maximum [Member]
Debt Instrument [Line Items]
Debt maturity year	2097
Finance and Financial Products [Member]
Debt Instrument [Line Items]
Notes payable and other borrowings	$ 10,755	13,085
Finance and Financial Products [Member] \| Subsidiaries [Member] \| Berkshire Hathaway Finance Corporation [Member]
Debt Instrument [Line Items]
Weighted average interest rate, percentage	3.10%
Notes payable and other borrowings	$ 10,578	12,926
Finance and Financial Products [Member] \| Subsidiaries [Member] \| Berkshire Hathaway Finance Corporation [Member] \| Minimum [Member]
Debt Instrument [Line Items]
Debt maturity year	2018
Finance and Financial Products [Member] \| Subsidiaries [Member] \| Berkshire Hathaway Finance Corporation [Member] \| Maximum [Member]
Debt Instrument [Line Items]
Debt maturity year	2043
Finance and Financial Products [Member] \| Subsidiaries [Member] \| Other Subsidiaries [Member]
Debt Instrument [Line Items]
Weighted average interest rate, percentage	4.00%
Notes payable and other borrowings	$ 177	159
Finance and Financial Products [Member] \| Subsidiaries [Member] \| Other Subsidiaries [Member] \| Minimum [Member]
Debt Instrument [Line Items]
Debt maturity year	2019
Finance and Financial Products [Member] \| Subsidiaries [Member] \| Other Subsidiaries [Member] \| Maximum [Member]
Debt Instrument [Line Items]
Debt maturity year	2028
Insurance and Other [Member]
Debt Instrument [Line Items]
Notes payable and other borrowings	$ 25,663	27,324
Insurance and Other [Member] \| Subsidiaries [Member]
Debt Instrument [Line Items]
Short-term debt, weighted average interest rate	3.70%
Weighted average interest rate, percentage	4.00%
Short-term debt	$ 1,800	1,832
Other borrowings	$ 5,676	6,725
Insurance and Other [Member] \| Subsidiaries [Member] \| Minimum [Member]
Debt Instrument [Line Items]
Debt maturity year	2018
Insurance and Other [Member] \| Subsidiaries [Member] \| Maximum [Member]
Debt Instrument [Line Items]
Debt maturity year	2045
Insurance and Other [Member] \| Berkshire Hathaway Inc. (Parent) [Member] \| U.S. Dollar Denominated [Member]
Debt Instrument [Line Items]
Weighted average interest rate, percentage	3.00%
Notes payable and other borrowings	$ 9,804	10,603
Insurance and Other [Member] \| Berkshire Hathaway Inc. (Parent) [Member] \| Euro Denominated [Member]
Debt Instrument [Line Items]
Weighted average interest rate, percentage	1.10%
Notes payable and other borrowings	$ 8,383	$ 8,164
Insurance and Other [Member] \| Berkshire Hathaway Inc. (Parent) [Member] \| Minimum [Member] \| U.S. Dollar Denominated [Member]
Debt Instrument [Line Items]
Debt maturity year	2018
Insurance and Other [Member] \| Berkshire Hathaway Inc. (Parent) [Member] \| Minimum [Member] \| Euro Denominated [Member]
Debt Instrument [Line Items]
Debt maturity year	2020
Insurance and Other [Member] \| Berkshire Hathaway Inc. (Parent) [Member] \| Maximum [Member] \| U.S. Dollar Denominated [Member]
Debt Instrument [Line Items]
Debt maturity year	2047
Insurance and Other [Member] \| Berkshire Hathaway Inc. (Parent) [Member] \| Maximum [Member] \| Euro Denominated [Member]
Debt Instrument [Line Items]
Debt maturity year	2035

Year the debt matures, in CCYY format.

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- Definition

Sum of the carrying values as of the balance sheet date of all debt, including all short-term borrowings, long-term debt, and capital lease obligations.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-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=6876686&loc=d3e534808-122878

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
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-Section S99
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-URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910

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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

No definition available.

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Weighted average interest rate of debt outstanding.

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No definition available.

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- Definition

Amount of long-term debt and capital lease obligation due after one year or beyond the normal operating cycle, if longer.

+ References

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Reflects the total carrying amount as of the balance sheet date of debt having initial terms less than one year or the normal operating cycle, if longer.

+ 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(19)(a))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
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-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03(a)(16)(a)(1))
-URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910

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- Definition

Weighted average interest rate of short-term debt outstanding calculated at point in time.

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- Definition

Including the current and noncurrent portions, carrying value as of the balance sheet date of uncollateralized debt obligations (with maturities initially due after one year or beyond the operating cycle if longer).

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03(a)(16))
-URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
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-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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