Notes payable and other borrowings - Narrative (Detail) (USD $)	12 Months Ended									1 Months Ended	12 Months Ended				1 Months Ended	12 Months Ended	1 Months Ended	12 Months Ended	1 Months Ended				12 Months Ended		1 Months Ended			1 Months Ended			1 Months Ended		12 Months Ended			6 Months Ended	12 Months Ended			5 Months Ended	12 Months Ended			1 Months Ended
	Dec. 31, 2012 Insurance and Other [Member]	Dec. 31, 2011 Insurance and Other [Member]	Dec. 31, 2010 Insurance and Other [Member]	Dec. 31, 2012 Railroad, Utilities and Energy [Member]	Dec. 31, 2011 Railroad, Utilities and Energy [Member]	Dec. 31, 2010 Railroad, Utilities and Energy [Member]	Dec. 31, 2012 Finance and Financial Products [Member]	Dec. 31, 2011 Finance and Financial Products [Member]	Dec. 31, 2010 Finance and Financial Products [Member]	Feb. 28, 2011 Berkshire Hathaway (Parent) [Member]	Dec. 31, 2012 Berkshire Hathaway (Parent) [Member]	Dec. 31, 2011 Berkshire Hathaway (Parent) [Member]	Dec. 31, 2010 Berkshire Hathaway (Parent) [Member]	Dec. 31, 2012 Berkshire Hathaway (Parent) [Member] Subsidiaries Excluding Berkshire Hathaway Finance Corporation [Member]	Jan. 31, 2012 Berkshire Hathaway (Parent) [Member] Senior Notes Due 2017 at 1.9% [Member] Insurance and Other [Member]	Dec. 31, 2012 Berkshire Hathaway (Parent) [Member] Senior Notes Due 2017 at 1.9% [Member] Insurance and Other [Member]	Jan. 31, 2012 Berkshire Hathaway (Parent) [Member] Senior Notes Due 2022 at 3.4% [Member] Insurance and Other [Member]	Dec. 31, 2012 Berkshire Hathaway (Parent) [Member] Senior Notes Due 2022 at 3.4% [Member] Insurance and Other [Member]	Feb. 29, 2012 Berkshire Hathaway (Parent) [Member] Senior Notes Due 2012 [Member]	Feb. 29, 2012 Berkshire Hathaway (Parent) [Member] Senior Notes Due 2012 [Member] Insurance and Other [Member]	Aug. 31, 2011 Berkshire Hathaway (Parent) [Member] Senior Notes [Member]	Feb. 28, 2010 Berkshire Hathaway (Parent) [Member] Senior Notes [Member]	Dec. 31, 2012 Berkshire Hathaway (Parent) [Member] Senior Notes [Member]	Dec. 31, 2012 Berkshire Hathaway (Parent) [Member] Senior Notes [Member] Maximum [Member]	Jan. 31, 2013 Berkshire Hathaway (Parent) [Member] Financing Transactions [Member] Senior Notes [Member]	Jan. 31, 2013 Berkshire Hathaway (Parent) [Member] Financing Transactions [Member] Senior Notes [Member] Minimum [Member]	Jan. 31, 2013 Berkshire Hathaway (Parent) [Member] Financing Transactions [Member] Senior Notes [Member] Maximum [Member]	Jan. 31, 2013 Berkshire Hathaway (Parent) [Member] Financing Transactions [Member] Senior Notes [Member] Insurance and Other [Member]	Jan. 31, 2013 Berkshire Hathaway (Parent) [Member] Financing Transactions [Member] Senior Notes [Member] Insurance and Other [Member] Minimum [Member]	Jan. 31, 2013 Berkshire Hathaway (Parent) [Member] Financing Transactions [Member] Senior Notes [Member] Insurance and Other [Member] Maximum [Member]	Feb. 28, 2013 Berkshire Hathaway (Parent) [Member] Financing Transactions [Member] Senior Notes Due 2013 and 2014 [Member]	Feb. 28, 2013 Berkshire Hathaway (Parent) [Member] Financing Transactions [Member] Senior Notes Due 2013 and 2014 [Member] Insurance and Other [Member]	Dec. 31, 2012 MidAmerican Subsidiaries [Member] Long-term Debt [Member] Railroad, Utilities and Energy [Member]	Dec. 31, 2012 MidAmerican Subsidiaries [Member] Long-term Debt [Member] Railroad, Utilities and Energy [Member] Minimum [Member]	Dec. 31, 2012 MidAmerican Subsidiaries [Member] Long-term Debt [Member] Railroad, Utilities and Energy [Member] Maximum [Member]	Aug. 31, 2012 BNSF [Member] Debentures [Member] Railroad, Utilities and Energy [Member]	Dec. 31, 2012 BNSF [Member] Debentures [Member] Railroad, Utilities and Energy [Member]	Aug. 31, 2012 BNSF [Member] Debentures [Member] Railroad, Utilities and Energy [Member] Minimum [Member]	Aug. 31, 2012 BNSF [Member] Debentures [Member] Railroad, Utilities and Energy [Member] Maximum [Member]	Sep. 30, 2012 Berkshire Hathaway Finance Corporation [Member] Senior Notes [Member] Finance and Financial Products [Member]	Dec. 31, 2012 Berkshire Hathaway Finance Corporation [Member] Senior Notes [Member] Finance and Financial Products [Member]	Sep. 30, 2012 Berkshire Hathaway Finance Corporation [Member] Senior Notes [Member] Finance and Financial Products [Member] Minimum [Member]	Sep. 30, 2012 Berkshire Hathaway Finance Corporation [Member] Senior Notes [Member] Finance and Financial Products [Member] Maximum [Member]	Jan. 31, 2013 Berkshire Hathaway Finance Corporation [Member] Financing Transactions [Member] Senior Notes [Member] Finance and Financial Products [Member]	Dec. 31, 2012 Berkshire Hathaway Subsidiaries [Member] Line of Credit and Commercial Paper Facilities [Member]
Debt Instrument [Line Items]
Principal amount of debt issued															$ 1,100,000,000		$ 600,000,000				$ 2,000,000,000	$ 8,000,000,000			$ 2,600,000,000			$ 2,600,000,000								$ 2,500,000,000				$ 2,350,000,000				$ 500,000,000
Issuance date																January 2012		January 2012							January 2013			January 2013									March and August 2012				May and September 2012
Debt Instrument, Interest Rate, Stated Percentage																1.90%		3.40%						3.75%		0.80%	4.50%		0.80%	4.50%				1.43%	5.75%			3.05%	4.40%			1.60%	4.40%
Repayment of debt	2,078,000,000	2,307,000,000	430,000,000	2,119,000,000	2,335,000,000	777,000,000	3,131,000,000	1,959,000,000	2,417,000,000	2,000,000,000									1,700,000,000	1,700,000,000											2,600,000,000	2,600,000,000	1,600,000,000				500,000,000				2,700,000,000
Maturity date, range, start																							2014		2016			2016					2013			2022				2017
Maturity date, range, end																							2021		2043			2043					2042			2042				2042
Principal amount of debt issued or acquired																																	3,100,000,000
Repayment of debt											1,751,000,000	2,094,000,000	117,000,000																															500,000,000
Unused lines of credit available																																													4,100,000,000
Guarantee obligation														$ 4,000,000,000