Significant business acquisitions - Pro forma consolidated earnings data (Detail) (NV Energy, IMI plc, Lubrizol Specialty Products Inc. and WPLG Inc. [Member], USD $) In Millions, except Per Share data, unless otherwise specified	9 Months Ended
	Sep. 30, 2013
NV Energy, IMI plc, Lubrizol Specialty Products Inc. and WPLG Inc. [Member]
Business Acquisition [Line Items]
Revenues	$ 138,168
Net earnings attributable to Berkshire Hathaway shareholders	$ 14,805
Net earnings per equivalent Class A common share attributable to Berkshire Hathaway shareholders	$ 9,008