Business segment data - Earnings before income taxes (Detail) (USD $) In Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2011	Sep. 30, 2010	Sep. 30, 2011	Sep. 30, 2010
Segment Reporting Information [Line Items]
Earnings before income taxes	$ 5,950	$ 4,359	$ 12,802	$ 12,706
Reconciliation of segments to consolidated amount:
Total earnings before income taxes	3,363	4,534	10,862	12,570
Geico [Member]
Segment Reporting Information [Line Items]
Earnings before income taxes	114	289	610	917
General Re [Member]
Segment Reporting Information [Line Items]
Earnings before income taxes	148	201	(46)	384
Berkshire Hathaway Reinsurance Group [Member]
Segment Reporting Information [Line Items]
Earnings before income taxes	1,375	(237)	(322)	(68)
Berkshire Hathaway Primary Group [Member]
Segment Reporting Information [Line Items]
Earnings before income taxes	58	52	168	133
Insurance Group [Member]
Segment Reporting Information [Line Items]
Net investment income	1,038	1,218	3,703	3,995
Earnings before income taxes	2,733	1,523	4,113	5,361
BNSF [Member]
Segment Reporting Information [Line Items]
Earnings before income taxes	1,236	1,127	3,271	2,577	[1]
Finance and Financial Products [Member]
Segment Reporting Information [Line Items]
Earnings before income taxes	147	148	480	433
Marmon [Member]
Segment Reporting Information [Line Items]
Earnings before income taxes	257	212	752	621
McLane Company [Member]
Segment Reporting Information [Line Items]
Earnings before income taxes	124	89	311	278
MidAmerican [Member]
Segment Reporting Information [Line Items]
Earnings before income taxes	489	416	1,260	1,149
Other Businesses [Member]
Segment Reporting Information [Line Items]
Earnings before income taxes	964	844	2,615	2,287
Investment and derivative gain / loss [Member]
Reconciliation of segments to consolidated amount:
Total earnings before income taxes	(2,351)	312	(1,382)	248
Interest expense, excluding interest allocated to operating businesses [Member]
Reconciliation of segments to consolidated amount:
Total earnings before income taxes	(61)	(53)	(162)	(155)
Eliminations and other [Member]
Reconciliation of segments to consolidated amount:
Total earnings before income taxes	$ (175)	$ (84)	$ (396)	$ (229)

[1] Includes revenues and earnings from February 13, 2010.