Business segment data (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended										12 Months Ended
	Dec. 31, 2011		Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2010		Sep. 30, 2010	Jun. 30, 2010	Mar. 31, 2010	Dec. 31, 2011		Dec. 31, 2010		Dec. 31, 2009
Segment Reporting Information [Line Items]
Revenues											$ 144,080		$ 133,173		$ 110,802
Total revenues	37,955		33,739	38,274	33,720	36,165		36,274	31,709	32,037	143,688		136,185		112,493
Earnings before income taxes from operating businesses											17,184		17,271		11,158
Total earnings before income taxes											15,314		19,051		11,552
Capital expenditures											8,191		5,980		4,937
Depreciation of tangible assets											4,683		4,279		3,127
Identifiable assets at year-end	331,546					315,632					331,546		315,632		256,302
Total assets	392,647					372,229					392,647		372,229		297,119
Goodwill at year-end	53,213					49,006					53,213		49,006		33,972
Geico [Member]
Segment Reporting Information [Line Items]
Premiums earned											15,363		14,283		13,576
Earnings before income taxes from operating businesses											576		1,117		649
Identifiable assets at year-end	27,253					25,631					27,253		25,631		22,996
Goodwill at year-end	1,372					1,372					1,372		1,372
General Re [Member]
Segment Reporting Information [Line Items]
Premiums earned											5,816		5,693		5,829
Earnings before income taxes from operating businesses											144		452		477
Identifiable assets at year-end	28,442					29,196					28,442		29,196		30,894
Goodwill at year-end	13,532					13,532					13,532		13,532
Berkshire Hathaway Reinsurance Group [Member]
Segment Reporting Information [Line Items]
Premiums earned											9,147		9,076		6,706
Earnings before income taxes from operating businesses											(714)		176		250
Berkshire Hathaway Primary Group [Member]
Segment Reporting Information [Line Items]
Premiums earned											1,749		1,697		1,773
Earnings before income taxes from operating businesses											242		268		84
Berkshire Hathaway Insurance Group Investment Income [Member]
Segment Reporting Information [Line Items]
Interest, dividend and other investment income											4,746		5,186		5,509
Earnings before income taxes from operating businesses											4,725		5,145		5,459
Berkshire Hathaway Insurance Group [Member]
Segment Reporting Information [Line Items]
Revenues											36,821		35,935		33,393
Earnings before income taxes from operating businesses											4,973		7,158		6,919
Capital expenditures											40		40		50
Depreciation of tangible assets											56		66		71
Identifiable assets at year-end	160,608					159,210					160,608		159,210		156,677
Goodwill at year-end	15,511					15,493					15,511		15,493
BNSF [Member]
Segment Reporting Information [Line Items]
Revenues											19,548	[1]	15,059	[1]
Earnings before income taxes from operating businesses											4,741	[1]	3,611	[1]
Capital expenditures											3,325	[1]	1,829	[1]
Depreciation of tangible assets											1,480	[1]	1,221	[1]
Identifiable assets at year-end	55,282					53,476					55,282		53,476
Goodwill at year-end	14,803					14,803					14,803		14,803
Finance and Financial Products Reportable Segment [Member]
Segment Reporting Information [Line Items]
Revenues											4,014		4,264		4,301
Earnings before income taxes from operating businesses											774		689		653
Capital expenditures											331		233		148
Depreciation of tangible assets											180		204		219
Identifiable assets at year-end	23,919					24,692					23,919		24,692		24,027
Goodwill at year-end	1,032					1,031					1,032		1,031
Marmon [Member]
Segment Reporting Information [Line Items]
Revenues											6,925		5,967		5,067
Earnings before income taxes from operating businesses											992		813		686
Capital expenditures											514		307		436
Depreciation of tangible assets											484		507		521
Identifiable assets at year-end	10,597					10,047					10,597		10,047		9,768
Goodwill at year-end	727					709					727		709
McLane Company [Member]
Segment Reporting Information [Line Items]
Revenues											33,279		32,687		31,207
Earnings before income taxes from operating businesses											370		369		344
Capital expenditures											188		166		172
Depreciation of tangible assets											129		129		120
Identifiable assets at year-end	4,107					4,018					4,107		4,018		3,505
Goodwill at year-end	155					155					155		155
MidAmerican [Member]
Segment Reporting Information [Line Items]
Revenues											11,291		11,305		11,443
Earnings before income taxes from operating businesses											1,659		1,539		1,528
Capital expenditures											2,684		2,593		3,413
Depreciation of tangible assets											1,333		1,262		1,246
Identifiable assets at year-end	42,039					40,045					42,039		40,045		39,437
Goodwill at year-end	5,253					5,281					5,253		5,281
Other Businesses [Member]
Segment Reporting Information [Line Items]
Revenues											32,202	[2]	27,956	[2]	25,391	[2]
Earnings before income taxes from operating businesses											3,675	[2]	3,092	[2]	1,028	[2]
Capital expenditures											1,109	[2]	812	[2]	718	[2]
Depreciation of tangible assets											1,021	[2]	890	[2]	950	[2]
Identifiable assets at year-end	34,994	[3]				24,144	[3]				34,994	[3]	24,144	[3]	22,888	[3]
Goodwill at year-end	15,732	[3]				11,534	[3]				15,732	[3]	11,534	[3]
Not Allocated to Segments [Member]
Segment Reporting Information [Line Items]
Investment and derivative gains/losses											(830)		2,346		787
Interest expense											(221)		(208)		(101)
Identifiable assets at year-end	7,888					7,591					7,888		7,591		6,845
Intersegment Eliminations and Other Reconciling Items [Member]
Segment Reporting Information [Line Items]
Total revenues											438		666		904
Earnings before income taxes from operating businesses											(819)		(358)		(292)
Berkshire Hathaway Reinsurance and Primary Groups [Member]
Segment Reporting Information [Line Items]
Identifiable assets at year-end	104,913					104,383					104,913		104,383		102,787
Goodwill at year-end	$ 607					$ 589					$ 607		$ 589

[1] From acquisition date of February 12, 2010.

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

[3] Includes Lubrizol, acquired in 2011.