Notes payable and other borrowings (Detail) (USD $) In Millions, unless otherwise specified					9 Months Ended			9 Months Ended			9 Months Ended					9 Months Ended			9 Months Ended					9 Months Ended			9 Months Ended
	Sep. 30, 2013 Railroad, Utilities and Energy [Member]	Dec. 31, 2012 Railroad, Utilities and Energy [Member]	Sep. 30, 2013 Railroad, Utilities and Energy [Member] MidAmerican [Member]	Dec. 31, 2012 Railroad, Utilities and Energy [Member] MidAmerican [Member]	Sep. 30, 2013 Railroad, Utilities and Energy [Member] MidAmerican [Member] Debt [Member]	Sep. 30, 2013 Railroad, Utilities and Energy [Member] MidAmerican Subsidiaries [Member]	Dec. 31, 2012 Railroad, Utilities and Energy [Member] MidAmerican Subsidiaries [Member]	Sep. 30, 2013 Railroad, Utilities and Energy [Member] MidAmerican Subsidiaries [Member] Debt [Member]	Sep. 30, 2013 Railroad, Utilities and Energy [Member] BNSF [Member]	Dec. 31, 2012 Railroad, Utilities and Energy [Member] BNSF [Member]	Sep. 30, 2013 Railroad, Utilities and Energy [Member] BNSF [Member] Debt [Member]	Sep. 30, 2013 Finance and Financial Products [Member]	Dec. 31, 2012 Finance and Financial Products [Member]	Sep. 30, 2013 Finance and Financial Products [Member] Berkshire Hathaway Finance Corporation [Member]	Dec. 31, 2012 Finance and Financial Products [Member] Berkshire Hathaway Finance Corporation [Member]	Sep. 30, 2013 Finance and Financial Products [Member] Berkshire Hathaway Finance Corporation [Member] Debt [Member]	Sep. 30, 2013 Finance and Financial Products [Member] Other Finance Subsidiaries [Member]	Dec. 31, 2012 Finance and Financial Products [Member] Other Finance Subsidiaries [Member]	Sep. 30, 2013 Finance and Financial Products [Member] Other Finance Subsidiaries [Member] Debt [Member]	Sep. 30, 2013 Insurance and Other [Member]	Dec. 31, 2012 Insurance and Other [Member]	Sep. 30, 2013 Insurance and Other [Member] Berkshire Hathaway (Parent) [Member]	Dec. 31, 2012 Insurance and Other [Member] Berkshire Hathaway (Parent) [Member]	Sep. 30, 2013 Insurance and Other [Member] Berkshire Hathaway (Parent) [Member] Debt [Member]	Sep. 30, 2013 Insurance and Other [Member] Insurance and Other Subsidiaries [Member]	Dec. 31, 2012 Insurance and Other [Member] Insurance and Other Subsidiaries [Member]	Sep. 30, 2013 Insurance and Other [Member] Insurance and Other Subsidiaries [Member] Debt [Member]
Notes payable and other borrowings [Line Items]
Maturity date, range, start					2014			2013			2013					2013			2013					2013			2013
Maturity date, range, end					2037			2043			2097					2043			2036					2047			2035
Short-term debt, weighted average interest rate																									0.30%
Senior unsecured debt			$ 4,621	$ 4,621
Weighted Average Interest Rate, percentage			6.30%			5.00%			5.30%					3.50%			4.70%					2.70%			5.90%
Notes payable and other borrowings	40,016	36,156				18,329	17,002		17,066	14,533		12,710	13,045	11,182	11,186		1,528	1,859		13,023	13,535	8,305	8,323
Short-term borrowings																									1,063	1,416
Other borrowings																									$ 3,655	$ 3,796