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This element represents amounts recorded to regulatory assets and liabilities arising from net derivative contract liabilities measured at fair value on a recurring basis using unobservable inputs (Level 3).

+ References

No definition available.

+ Details

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Namespace Prefix:	brka_
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Balance Type:	debit
Period Type:	duration

- Definition

Amount of gain (loss) recognized in earnings, arising from assets measured at fair value on a recurring basis using unobservable inputs (level 3).

+ References

+ Details

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- Definition

Amount of gain (loss) recognized in other comprehensive income, arising from assets measured at fair value on a recurring basis using unobservable inputs (level 3).

+ References

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- Definition

Amount of purchases, sales, issues, and settlements (net) which have taken place in relation to assets measured at fair value on a recurring basis using unobservable inputs (level 3).

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 157

-Paragraph 32

-Subparagraph c(2)

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

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- Definition

Sales that have taken place during the period in relation to assets measured at fair value and categorized within Level 3 of the fair value hierarchy.

+ References

+ Details

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- Definition

This element represents [net] transfers in to and out of assets measured at fair value on a recurring basis using unobservable inputs (Level 3) which have taken place during the period.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 157

-Paragraph 32

-Subparagraph c(3)

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

+ Details

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- Definition

This element represents an asset measured at fair value using significant unobservable inputs (Level 3) which is required for reconciliation purposes of beginning and ending balances.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 820

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (c)

-URI http://asc.fasb.org/extlink&oid=7578670&loc=d3e19207-110258

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-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 157

-Paragraph 32

-Subparagraph c

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

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Data Type:	xbrli:monetaryItemType
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Period Type:	instant

- Definition

Amount of gain (loss) recognized in earnings, arising from liabilities measured at fair value on a recurring basis using unobservable inputs (level 3).

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 820

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (c)(1)

-URI http://asc.fasb.org/extlink&oid=7578670&loc=d3e19207-110258

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-Publisher FASB

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-Number 157

-Paragraph 32

-Subparagraph c(1)

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

+ Details

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Period Type:	duration

- Definition

Amount of gain (loss) recognized in other comprehensive income, arising from liabilities measured at fair value on a recurring basis using unobservable inputs (level 3).

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 820

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (c)(1a)

-URI http://asc.fasb.org/extlink&oid=7578670&loc=d3e19207-110258

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-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 157

-Paragraph 32

-Subparagraph c(1)

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

+ Details

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

- Definition

Amount of purchases, sales, issues, and settlements in relation to liabilities measured at fair value on a recurring basis using unobservable inputs (level 3).

+ References

+ Details

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- Definition

Settlements that have taken place during the period in relation to liabilities measured at fair value and categorized within Level 3 of the fair value hierarchy.

+ References

+ Details

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Balance Type:	debit
Period Type:	duration

- Definition

This element represents a liability measured at fair value using significant unobservable inputs (Level 3) which is required for reconciliation purposes of beginning and ending balances.

+ References

+ Details

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Fair value measurements - Significant unobservable inputs (Detail) (Significant Unobservable Inputs (Level 3) [Member], USD $) In Millions, unless otherwise specified	3 Months Ended							3 Months Ended
	Mar. 31, 2013 Net Derivative Contract (Liabilities) [Member]	Mar. 31, 2012 Net Derivative Contract (Liabilities) [Member]	Mar. 31, 2013 Fixed Maturities [Member]	Mar. 31, 2012 Fixed Maturities [Member]	Mar. 31, 2012 Equity Securities [Member]	Mar. 31, 2013 Equity Securities [Member]	Dec. 31, 2012 Equity Securities [Member]	Mar. 31, 2013 Other Fixed Maturities and Equity Securities [Member]	Mar. 31, 2012 Other Fixed Maturities and Equity Securities [Member]
Fair value measurements Significant unobservable inputs [Line Items]
Beginning Balance	$ (7,847)	$ (9,908)
Gains (losses) included in earnings	1,235	1,022
Gains (losses) included in other comprehensive income	(3)	(3)
Gains (losses) included in regulatory assets and liabilities	1	9
Settlements, net	(27)
Acquisitions, dispositions and settlements		31
Ending Balance	(6,641)	(8,849)
Beginning Balance			652	784	22	35	35	15,750	11,669
Gains (losses) included in earnings					(1)			520
Gains (losses) included in other comprehensive income			(2)	6	11			399	2,489
Acquisitions, dispositions and settlements				(6)
Dispositions			(1)
Transfers into (out of) Level 3				(129)
Ending Balance			$ 649	$ 655	$ 32	$ 35	$ 35	$ 16,669	$ 14,158