Business segment data (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended				9 Months Ended
	Sep. 30, 2012		Sep. 30, 2011		Sep. 30, 2012		Sep. 30, 2011
Segment Reporting Information [Line Items]
Revenues	$ 40,202		$ 35,969		$ 116,748		$ 106,744
Total revenues	41,050		33,739		117,743		105,733
Earnings before income taxes from operating businesses	5,442		5,950		15,633		12,802
Total earnings before income taxes	5,936		3,363		15,482		10,862
Geico [Member]
Segment Reporting Information [Line Items]
Premiums earned	4,240		3,907		12,388		11,400
Earnings before income taxes from operating businesses	435		114		714		610
General Re [Member]
Segment Reporting Information [Line Items]
Premiums earned	1,445		1,438		4,342		4,319
Earnings before income taxes from operating businesses	154		148		373		(46)
Berkshire Hathaway Reinsurance Group [Member]
Segment Reporting Information [Line Items]
Premiums earned	2,578		1,839		6,983		7,051
Earnings before income taxes from operating businesses	(102)		1,375		320		(322)
Berkshire Hathaway Primary Group [Member]
Segment Reporting Information [Line Items]
Premiums earned	588		461		1,631		1,306
Earnings before income taxes from operating businesses	121		58		243		168
Berkshire Hathaway Insurance Group Investment Income [Member]
Segment Reporting Information [Line Items]
Interest, dividend and other investment income	981		1,042		3,436		3,718
Earnings before income taxes from operating businesses	976		1,038		3,421		3,703
Berkshire Hathaway Insurance Group [Member]
Segment Reporting Information [Line Items]
Revenues	9,832		8,687		28,780		27,794
Earnings before income taxes from operating businesses	1,584		2,733		5,071		4,113
BNSF [Member]
Segment Reporting Information [Line Items]
Revenues	5,343		4,961		15,407		14,284
Earnings before income taxes from operating businesses	1,508		1,236		3,903		3,271
Finance and Financial Products Reportable Segment [Member]
Segment Reporting Information [Line Items]
Revenues	1,006		995		2,981		2,899
Earnings before income taxes from operating businesses	175		147		527		480
Marmon [Member]
Segment Reporting Information [Line Items]
Revenues	1,795		1,800		5,451		5,255
Earnings before income taxes from operating businesses	293		257		869		752
McLane Company [Member]
Segment Reporting Information [Line Items]
Revenues	9,534		8,708		26,611		24,919
Earnings before income taxes from operating businesses	130		124		305		311
MidAmerican [Member]
Segment Reporting Information [Line Items]
Revenues	3,076		2,867		8,718		8,425
Earnings before income taxes from operating businesses	542		489		1,349		1,260
Other Businesses [Member]
Segment Reporting Information [Line Items]
Revenues	9,616	[1]	7,951	[1]	28,800	[1]	23,168	[1]
Earnings before income taxes from operating businesses	1,210	[1]	964	[1]	3,609	[1]	2,615	[1]
Not Allocated to Segments [Member]
Segment Reporting Information [Line Items]
Investment and derivative gains/losses	799		(2,351)		752		(1,382)
Interest expense	(52)		(61)		(196)		(162)
Intersegment Eliminations and Other Reconciling Items [Member]
Segment Reporting Information [Line Items]
Total revenues	49		121		243		371
Earnings before income taxes from operating businesses	$ (253)		$ (175)		$ (707)		$ (396)

[1] Includes Lubrizol from the acquisition date of September 16, 2011.