Significant business acquisitions - Pro forma consolidated earnings data (Detail) (NV Energy, AltaLink, IMI plc, Lubrizol Specialty Products Inc. and WPLG Inc. [Member], USD $) In Millions, except Per Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013
NV Energy, AltaLink, IMI plc, Lubrizol Specialty Products Inc. and WPLG Inc. [Member]
Business Acquisition [Line Items]
Revenues	$ 195,298	$ 186,664
Net earnings attributable to Berkshire Hathaway shareholders	$ 19,975	$ 19,845
Net earnings per equivalent Class A common share attributable to Berkshire Hathaway shareholders	$ 12,154	$ 12,074