Notes payable and other borrowings - Narrative (Detail) (USD $)	9 Months Ended							1 Months Ended	9 Months Ended			1 Months Ended	9 Months Ended		1 Months Ended		9 Months Ended	1 Months Ended		1 Months Ended		1 Months Ended		1 Months Ended			1 Months Ended			9 Months Ended	1 Months Ended	9 Months Ended
	Sep. 30, 2013 Insurance and Other [Member]	Sep. 30, 2012 Insurance and Other [Member]	Sep. 30, 2013 Railroad, Utilities and Energy [Member]	Sep. 30, 2012 Railroad, Utilities and Energy [Member]	Sep. 30, 2013 Finance and Financial Products [Member]	Sep. 30, 2012 Finance and Financial Products [Member]	Sep. 30, 2013 Berkshire Hathaway (Parent) [Member] Subsidiaries Excluding Berkshire Hathaway Finance Corporation [Member]	Jan. 31, 2013 Berkshire Hathaway (Parent) [Member] Senior Notes [Member] Insurance and Other [Member]	Sep. 30, 2013 Berkshire Hathaway (Parent) [Member] Senior Notes [Member] Insurance and Other [Member]	Sep. 30, 2013 Berkshire Hathaway (Parent) [Member] Senior Notes [Member] Insurance and Other [Member] Minimum [Member]	Sep. 30, 2013 Berkshire Hathaway (Parent) [Member] Senior Notes [Member] Insurance and Other [Member] Maximum [Member]	Feb. 28, 2013 Berkshire Hathaway (Parent) [Member] Senior Notes Due 2013 and 2014 [Member] Insurance and Other [Member]	Sep. 30, 2013 MidAmerican Subsidiaries [Member] Term Debt [Member] Railroad, Utilities and Energy [Member]	Sep. 30, 2013 Mid American and Subsidiaries [Member] Railroad, Utilities and Energy [Member]	Aug. 31, 2013 BNSF [Member] Debentures [Member] Railroad, Utilities and Energy [Member]	Mar. 31, 2013 BNSF [Member] Debentures [Member] Railroad, Utilities and Energy [Member]	Sep. 30, 2013 BNSF [Member] Debentures [Member] Railroad, Utilities and Energy [Member]	Mar. 31, 2013 BNSF [Member] Debentures Due 2023 at 3.0% [Member] Railroad, Utilities and Energy [Member]	Sep. 30, 2013 BNSF [Member] Debentures Due 2023 at 3.0% [Member] Railroad, Utilities and Energy [Member]	Mar. 31, 2013 BNSF [Member] Debentures Due 2043 at 4.45% [Member] Railroad, Utilities and Energy [Member]	Sep. 30, 2013 BNSF [Member] Debentures Due 2043 at 4.45% [Member] Railroad, Utilities and Energy [Member]	Aug. 31, 2013 BNSF [Member] Debentures Due 2023 at 3.85% [Member] Railroad, Utilities and Energy [Member]	Sep. 30, 2013 BNSF [Member] Debentures Due 2023 at 3.85% [Member] Railroad, Utilities and Energy [Member]	Aug. 31, 2013 BNSF [Member] Debentures Due 2043 at 5.15% [Member] Railroad, Utilities and Energy [Member]	Sep. 30, 2013 BNSF [Member] Debentures Due 2043 at 5.15% [Member] Railroad, Utilities and Energy [Member]	Sep. 30, 2013 Berkshire Hathaway Subsidiaries [Member] Line of Credit and Commercial Paper Facilities [Member]	Aug. 31, 2013 Berkshire Hathaway Finance Corporation [Member] Senior Notes [Member] Finance and Financial Products [Member]	May 31, 2013 Berkshire Hathaway Finance Corporation [Member] Senior Notes [Member] Finance and Financial Products [Member]	Jan. 31, 2013 Berkshire Hathaway Finance Corporation [Member] Senior Notes [Member] Finance and Financial Products [Member]	Sep. 30, 2013 Berkshire Hathaway Finance Corporation [Member] Senior Notes [Member] Finance and Financial Products [Member]	Oct. 31, 2013 Berkshire Hathaway Finance Corporation [Member] Senior Notes [Member] Subsequent Event [Member] Finance and Financial Products [Member]	Sep. 30, 2013 Berkshire Hathaway Finance Corporation [Member] Senior Notes Due 2017 at 1.6% [Member] Finance and Financial Products [Member]	Sep. 30, 2013 Berkshire Hathaway Finance Corporation [Member] Senior Notes Due 2022 at 3.0% [Member] Finance and Financial Products [Member]	Sep. 30, 2013 Berkshire Hathaway Finance Corporation [Member] Senior Notes Due 2018 at 1.3% [Member] Finance and Financial Products [Member]	Sep. 30, 2013 Berkshire Hathaway Finance Corporation [Member] Senior Notes Due 2043 at 4.3% [Member] Finance and Financial Products [Member]	Sep. 30, 2013 Berkshire Hathaway Finance Corporation [Member] Senior Notes Due 2016 at 0.95% [Member] Finance and Financial Products [Member]	Sep. 30, 2013 Berkshire Hathaway Finance Corporation [Member] Senior Notes Due 2018 at 2.0% [Member] Finance and Financial Products [Member]
Debt Instrument [Line Items]
Principal amount of debt issued								$ 2,600,000,000					$ 2,500,000,000		$ 1,500,000,000	$ 1,500,000,000		$ 700,000,000		$ 800,000,000		$ 800,000,000		$ 700,000,000						$ 2,500,000,000	$ 950,000,000	$ 275,000,000	$ 225,000,000	$ 500,000,000	$ 500,000,000	$ 600,000,000	$ 400,000,000
Issuance date									January 2013								March and August 2013
Debt instrument, interest rate, stated percentage										0.80%	4.50%								3.00%		4.45%		3.85%		5.15%							1.60%	3.00%	1.30%	4.30%	0.95%	2.00%
Maturity date, range, start									2016
Maturity date, range, end									2043
Repayment of long-term debt	2,811,000,000	1,962,000,000	836,000,000	1,137,000,000	2,843,000,000	3,009,000,000						2,600,000,000
Repayment of debt														1,400,000,000													1,000,000,000	1,000,000,000	500,000,000		950,000,000
Unused lines of credit available																										5,900,000,000
Guarantee obligation							$ 4,100,000,000