Business segment data (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended				6 Months Ended
	Jun. 30, 2012		Jun. 30, 2011		Jun. 30, 2012		Jun. 30, 2011
Segment Reporting Information [Line Items]
Revenues	$ 39,408		$ 37,052		$ 76,546		$ 70,775
Total revenues	38,546		38,274		76,693		71,994
Earnings before income taxes from operating businesses	5,853		4,316		10,191		6,852
Total earnings before income taxes	4,615		5,265		9,546		7,499
Geico [Member]
Segment Reporting Information [Line Items]
Premiums earned	4,132		3,818		8,148		7,493
Earnings before income taxes from operating businesses	155		159		279		496
General Re [Member]
Segment Reporting Information [Line Items]
Premiums earned	1,426		1,444		2,897		2,881
Earnings before income taxes from operating businesses	138		132		219		(194)
Berkshire Hathaway Reinsurance Group [Member]
Segment Reporting Information [Line Items]
Premiums earned	2,334		3,268		4,405		5,212
Earnings before income taxes from operating businesses	613		(354)		422		(1,697)
Berkshire Hathaway Primary Group [Member]
Segment Reporting Information [Line Items]
Premiums earned	536		419		1,043		845
Earnings before income taxes from operating businesses	51		54		122		110
Berkshire Hathaway Insurance Group Investment Income [Member]
Segment Reporting Information [Line Items]
Interest, dividend and other investment income	1,399		1,410		2,455		2,676
Earnings before income taxes from operating businesses	1,393		1,404		2,445		2,665
Berkshire Hathaway Insurance Group [Member]
Segment Reporting Information [Line Items]
Revenues	9,827		10,359		18,948		19,107
Earnings before income taxes from operating businesses	2,350		1,395		3,487		1,380
BNSF [Member]
Segment Reporting Information [Line Items]
Revenues	5,062		4,790		10,064		9,323
Earnings before income taxes from operating businesses	1,280		1,070		2,395		2,035
Finance and Financial Products Reportable Segment [Member]
Segment Reporting Information [Line Items]
Revenues	1,016		991		1,975		1,904
Earnings before income taxes from operating businesses	189		177		352		333
Marmon [Member]
Segment Reporting Information [Line Items]
Revenues	1,863		1,781		3,656		3,455
Earnings before income taxes from operating businesses	307		273		576		495
McLane Company [Member]
Segment Reporting Information [Line Items]
Revenues	9,004		8,444		17,077		16,211
Earnings before income taxes from operating businesses	73		105		175		187
MidAmerican [Member]
Segment Reporting Information [Line Items]
Revenues	2,748		2,678		5,642		5,558
Earnings before income taxes from operating businesses	324		320		807		771
Other Businesses [Member]
Segment Reporting Information [Line Items]
Revenues	9,888	[1]	8,009	[1]	19,184	[1]	15,217	[1]
Earnings before income taxes from operating businesses	1,330	[1]	976	[1]	2,399	[1]	1,651	[1]
Not Allocated to Segments [Member]
Segment Reporting Information [Line Items]
Investment and derivative gains/losses	(943)		1,105		(47)		969
Interest expense	(78)		(50)		(144)		(101)
Intersegment Eliminations and Other Reconciling Items [Member]
Segment Reporting Information [Line Items]
Total revenues	81		117		194		250
Earnings before income taxes from operating businesses	$ (217)		$ (106)		$ (454)		$ (221)

[1] Includes Lubrizol in 2012.