Notes payable and other borrowings - Narrative (Detail) (USD $)	3 Months Ended						1 Months Ended				3 Months Ended				3 Months Ended			1 Months Ended
	Mar. 31, 2012 Insurance and Other [Member]	Mar. 31, 2011 Insurance and Other [Member]	Mar. 31, 2012 Railroad, Utilities and Energy [Member]	Mar. 31, 2011 Railroad, Utilities and Energy [Member]	Mar. 31, 2012 Finance and Financial Products [Member]	Mar. 31, 2011 Finance and Financial Products [Member]	Feb. 28, 2010 Berkshire Hathaway (Parent) [Member] Unsecured Debt [Member] Insurance and Other [Member]	Feb. 28, 2012 Berkshire Hathaway (Parent) [Member] Floating Rate and 1.4% Notes Due February 2012 [Member] Insurance and Other [Member]	Jan. 31, 2012 Berkshire Hathaway (Parent) [Member] Senior Notes Due In 2017 at 1.9% [Member] Insurance and Other [Member]	Jan. 31, 2012 Berkshire Hathaway (Parent) [Member] Senior Notes Due In 2022 at 3.4% [Member] Insurance and Other [Member]	Mar. 31, 2012 MidAmerican Subsidiaries [Member] Long-term Debt [Member] Railroad, Utilities and Energy [Member]	Mar. 31, 2012 MidAmerican Subsidiaries [Member] Long-term Debt [Member] Railroad, Utilities and Energy [Member] Minimum [Member]	Mar. 31, 2012 MidAmerican Subsidiaries [Member] Long-term Debt [Member] Railroad, Utilities and Energy [Member] Maximum [Member]	Mar. 31, 2012 MidAmerican [Member] Railroad, Utilities and Energy [Member]	Mar. 31, 2012 BNSF [Member] Debentures [Member] Railroad, Utilities and Energy [Member]	Mar. 31, 2012 BNSF [Member] Debentures Due March 2022 at 3.05% [Member] Railroad, Utilities and Energy [Member]	Mar. 31, 2012 BNSF [Member] Debentures Due March 2042 at 4.40% [Member] Railroad, Utilities and Energy [Member]	Jan. 31, 2012 Berkshire Hathaway Finance Corporation [Member] Finance and Financial Products [Member]	Mar. 31, 2012 Berkshire Hathaway Finance Corporation [Member] Finance and Financial Products [Member]	Mar. 31, 2012 Berkshire Hathaway Subsidiaries [Member] Line of Credit and Commercial Paper Facilities [Member]
Debt Instrument [Line Items]
Principal amount of debt issued							$ 8,000,000,000		$ 1,100,000,000	$ 600,000,000	$ 1,600,000,000				$ 1,250,000,000	$ 625,000,000	$ 625,000,000
Issuance date									January 2012	January 2012					March 2012	March 2012	March 2012
Debt Instrument, Interest Rate, Stated Percentage									1.90%	3.40%		2.95%	5.75%			3.05%	4.40%
Repayment of debt	1,791,000,000	2,143,000,000	160,000,000	276,000,000	333,000,000	1,590,000,000		1,700,000,000										250,000,000
Future repayments of debt scheduled in 2012														1,000,000,000					2,450,000,000
Maturity date, range, start											2015
Maturity date, range, end											2042
Unused lines of credit available																				$ 4,500,000,000