Business segment data (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Segment Reporting Information [Line Items]
Revenues	$ 46,541	$ 41,050	$ 135,101	$ 117,743
Total earnings before income taxes	7,378	5,936	21,564	15,482
Operating Businesses [Member]
Segment Reporting Information [Line Items]
Revenues	44,466	40,202	130,501	116,748
Earnings before income taxes from operating businesses	5,531	5,442	17,629	15,633
Operating Businesses [Member] | Geico [Member]
Segment Reporting Information [Line Items]
Premiums earned	4,730	4,240	13,726	12,388
Earnings before income taxes from operating businesses	307	435	909	714
Operating Businesses [Member] | General Re [Member]
Segment Reporting Information [Line Items]
Premiums earned	1,454	1,445	4,422	4,342
Earnings before income taxes from operating businesses	63	154	182	373
Operating Businesses [Member] | Berkshire Hathaway Reinsurance Group [Member]
Segment Reporting Information [Line Items]
Premiums earned	2,219	2,578	6,918	6,983
Earnings before income taxes from operating businesses	(206)	(102)	1,159	320
Operating Businesses [Member] | Berkshire Hathaway Primary Group [Member]
Segment Reporting Information [Line Items]
Premiums earned	867	588	2,396	1,631
Earnings before income taxes from operating businesses	99	121	228	243
Operating Businesses [Member] | Berkshire Hathaway Insurance Group Investment Income [Member]
Segment Reporting Information [Line Items]
Interest, dividend and other investment income	1,084	981	3,628	3,436
Earnings before income taxes from operating businesses	1,078	976	3,609	3,421
Operating Businesses [Member] | Berkshire Hathaway Insurance Group [Member]
Segment Reporting Information [Line Items]
Revenues	10,354	9,832	31,090	28,780
Earnings before income taxes from operating businesses	1,341	1,584	6,087	5,071
Operating Businesses [Member] | BNSF [Member]
Segment Reporting Information [Line Items]
Revenues	5,651	5,343	16,257	15,407
Earnings before income taxes from operating businesses	1,556	1,508	4,242	3,903
Operating Businesses [Member] | Finance and Financial Products Reportable Segment [Member]
Segment Reporting Information [Line Items]
Revenues	1,078	1,006	3,092	2,981
Earnings before income taxes from operating businesses	253	175	631	527
Operating Businesses [Member] | Marmon [Member]
Segment Reporting Information [Line Items]
Revenues	1,753	1,795	5,299	5,451
Earnings before income taxes from operating businesses	306	293	886	869
Operating Businesses [Member] | McLane Company [Member]
Segment Reporting Information [Line Items]
Revenues	11,547	9,534	33,707	26,611
Earnings before income taxes from operating businesses	126	130	372	305
Operating Businesses [Member] | MidAmerican [Member]
Segment Reporting Information [Line Items]
Revenues	3,392	3,076	9,564	8,718
Earnings before income taxes from operating businesses	586	542	1,574	1,349
Operating Businesses [Member] | Other Businesses [Member]
Segment Reporting Information [Line Items]
Revenues	10,691	9,616	31,492	28,800
Earnings before income taxes from operating businesses	1,363	1,210	3,837	3,609
Intersegment Eliminations and Other Reconciling Items [Member]
Segment Reporting Information [Line Items]
Investment and derivative gains/losses	2,141	799	4,805	752
Revenues	(66)	49	(205)	243
Interest expense	(80)	(52)	(226)	(196)
Earnings before income taxes from operating businesses	$ (214)	$ (253)	$ (644)	$ (707)