Other investments - Narrative (Detail) (USD $)	6 Months Ended		12 Months Ended	40 Months Ended		12 Months Ended		46 Months Ended	12 Months Ended		66 Months Ended		12 Months Ended	66 Months Ended				6 Months Ended	12 Months Ended	54 Months Ended	1 Months Ended	22 Months Ended	1 Months Ended		6 Months Ended		1 Months Ended		1 Months Ended	0 Months Ended		1 Months Ended		6 Months Ended	1 Months Ended		1 Months Ended
	Jun. 30, 2013	Jun. 30, 2013 Corporate Joint Venture [Member]	Dec. 31, 2008 Goldman Sachs Group Inc [Member] Other Investments [Member] Cumulative Perpetual Preferred Stock [Member]	Apr. 18, 2011 Goldman Sachs Group Inc [Member] Other Investments [Member] Cumulative Perpetual Preferred Stock [Member]	Jun. 30, 2013 Goldman Sachs Group Inc [Member] Other Investments [Member] Warrants Expiring October 1, 2013 [Member]	Dec. 31, 2008 Goldman Sachs Group Inc [Member] Other Investments [Member] Cumulative Perpetual Preferred Stock And Warrants [Member]	Dec. 31, 2008 General Electric Company [Member] Other Investments [Member] Cumulative Perpetual Preferred Stock [Member]	Oct. 17, 2011 General Electric Company [Member] Other Investments [Member] Cumulative Perpetual Preferred Stock [Member]	Dec. 31, 2008 General Electric Company [Member] Other Investments [Member] Cumulative Perpetual Preferred Stock And Warrants [Member]	Jun. 30, 2013 General Electric Company [Member] Other Investments [Member] Warrants Expiring October 16, 2013 [Member]	Jun. 30, 2013 Wm Wrigley Jr Company [Member] Other Investments [Member] Subordinated Debt Due 2018 [Member] Held-to-maturity Securities [Member]	Dec. 31, 2008 Wm Wrigley Jr Company [Member] Other Investments [Member] Subordinated Debt Due 2018 [Member] Held-to-maturity Securities [Member]	Dec. 31, 2008 Wm Wrigley Jr Company [Member] Other Investments [Member] Preferred Stock [Member] Available-for-sale Securities [Member]	Jun. 30, 2013 Wm Wrigley Jr Company [Member] Other Investments [Member] Preferred Stock [Member] Available-for-sale Securities [Member]	Jun. 30, 2013 Wm Wrigley Jr Company [Member] Other Investments [Member] Senior Notes Due 2013 and 2014 [Member] Held-to-maturity Securities [Member]	Dec. 31, 2009 Wm Wrigley Jr Company [Member] Other Investments [Member] Senior Notes Due 2013 and 2014 [Member] Held-to-maturity Securities [Member]	Jun. 30, 2013 Wm Wrigley Jr Company [Member] Other Investments [Member] Senior Notes Due 2013 and 2014 [Member] Held-to-maturity Securities [Member] Corporate Joint Venture [Member]	Jun. 30, 2013 The Dow Chemical Company [Member] Other Investments [Member] Series A Cumulative Convertible Perpetual Preferred Stock [Member]	Dec. 31, 2009 The Dow Chemical Company [Member] Other Investments [Member] Series A Cumulative Convertible Perpetual Preferred Stock [Member]	Jun. 30, 2013 The Dow Chemical Company [Member] Other Investments [Member] Series A Cumulative Convertible Perpetual Preferred Stock [Member]	Sep. 30, 2011 Bank of America Corporation [Member] Other Investments [Member] Cumulative Perpetual Preferred Stock [Member]	Jun. 30, 2013 Bank of America Corporation [Member] Other Investments [Member] Cumulative Perpetual Preferred Stock [Member]	Sep. 30, 2011 Bank of America Corporation [Member] Other Investments [Member] Cumulative Perpetual Preferred Stock And Warrants [Member]	Jun. 30, 2013 Bank of America Corporation [Member] Other Investments [Member] Warrants Expiring 2021 [Member]	Jun. 30, 2013 Goldman Sachs and General Electric [Member] Other Investments [Member] Common Stock Warrants [Member]	Jun. 30, 2013 Heinz Holding [Member] 3G Capital (venture partner) [Member]	Jun. 30, 2013 Heinz Holding [Member] Common Stock [Member] 3G Capital (venture partner) [Member]	Jun. 30, 2013 Heinz Holding [Member] Heinz [Member] Stock Options [Member] Management [Member]	Jun. 30, 2013 Heinz Holding [Member] Heinz [Member] 3G Capital (venture partner) [Member]	Jun. 07, 2013 Heinz Holding [Member] Heinz [Member] Common Stock [Member]	Jun. 30, 2013 Heinz Holding [Member] Other Investments [Member] Berkshire Hathaway (Parent) [Member]	Jun. 30, 2013 Heinz Holding [Member] Other Investments [Member] Common Stock [Member] Berkshire Hathaway (Parent) [Member]	Jun. 30, 2013 Heinz Holding [Member] Other Investments [Member] Cumulative Compounding Preferred Stock [Member]	Jun. 30, 2013 Heinz Holding [Member] Other Investments [Member] Cumulative Compounding Preferred Stock [Member]	Jun. 30, 2013 Heinz Holding [Member] Other Investments [Member] Common Stock, Cumulative Compounding Preferred Stock and Warrants [Member]	Jun. 30, 2013 Heinz Holding [Member] Other Investments [Member] Warrants Expiring June 7, 2018 [Member]	Jun. 30, 2013 Heinz Holding [Member] Other Investments [Member] Heinz [Member] Berkshire Hathaway (Parent) [Member]
Other Investments [Line Items]
Investment, number of shares purchased			50,000				30,000												3,000,000		50,000						425,000,000					425,000,000
Investment in preferred stock, stated dividend rate				10.00%				10.00%						5.00%						8.50%		6.00%											9.00%
Number of common shares that can be purchased					43,478,260					134,831,460														700,000,000												46,000,000
Amount paid for an investment	$ 12,250,000,000					$ 5,000,000,000			$ 3,000,000,000				$ 2,100,000,000						$ 3,000,000,000				$ 5,000,000,000												$ 12,250,000,000
Aggregate cost to exercise warrants					5,000,000,000					3,000,000,000														5,000,000,000
Exercise price for warrants, per share					$ 115					$ 22.25														$ 7.142857												$ 0.01
Aggregate net unrealized gains on securities																									728,000,000
Acquisition of debt investments, par value when acquired												4,400,000,000				1,000,000,000
Investment in notes, stated interest rate											11.45%
Investment owned, face value															800,000,000		200,000,000
Equity method investment ownership percentage		50.00%																								50.00%					50.00%
Conversion ratio of preferred stock into common stock																		24.201		24.201
Preferred stock conversion price, per share																		$ 41.32		$ 41.32
Common stock threshold price, per share, to trigger the issuer's option to convert preferred stock into common stock																		$ 53.72		$ 53.72
Minimum number of trading days in a consecutive-day period that the issuer's common stock price must exceed to trigger the issuer's option to convert preferred stock to common stock																		20 days
Range of trading days in a consecutive day period, number of days																		30 days
Redemption value of Cumulative Perpetual Preferred Stock, per share																						$ 105,000
Redemption value of Cumulative Perpetual Preferred Stock, aggregate value																						5,250,000,000
Business acquisition, cash price per share																														$ 72.50
Aggregate cash paid for acquiree's equity securities																											4,250,000,000			23,250,000,000
Investment in preferred stock, liquidation value																																	$ 8,000,000,000	$ 8,000,000,000
Common shares reserved for issuance under options to management of acquiree																												39,600,000
Investment in preferred stock, call feature																																		Callable after June 7, 2016 at the liquidation value plus an applicable premium and any accrued and unpaid dividends
Minimum percentage of initial common stock investment required to be held to maintain approval rights over significant transactions and governance																													66.00%								66.00%