Accumulated other comprehensive income (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Accumulated Other Comprehensive Income (Loss) [Line Items]
Ending Balance	$ 27,500	$ 17,654
Portion Attributable to Berkshire Hathaway Shareholders [Member] | Unrealized appreciation of investments [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	19,626	21,638	18,785
Other comprehensive income (loss)	9,647	(2,144)	2,838
Transactions with noncontrolling interests	(19)	132	15
Ending Balance	29,254	19,626	21,638
Portion Attributable to Berkshire Hathaway Shareholders [Member] | Foreign currency translation [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	(383)	(240)	(30)
Other comprehensive income (loss)	267	(144)	(193)
Transactions with noncontrolling interests	(4)	1	(17)
Ending Balance	(120)	(383)	(240)
Portion Attributable to Berkshire Hathaway Shareholders [Member] | Prior service and actuarial gains/losses of defined benefit plans [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	(1,589)	(853)	(824)
Other comprehensive income (loss)	(21)	(720)	(51)
Transactions with noncontrolling interests	9	(16)	22
Ending Balance	(1,601)	(1,589)	(853)
Portion Attributable to Berkshire Hathaway Shareholders [Member] | Other, including non controlling interests [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance		38	(138)
Other comprehensive income (loss)	(47)	3	195
Transactions with noncontrolling interests	14	(41)	(19)
Ending Balance	(33)		38
Portion Attributable to Berkshire Hathaway Shareholders [Member] | Accumulated other comprehensive income [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	17,654	20,583	17,793
Other comprehensive income (loss)	9,846	(3,005)	2,789
Transactions with noncontrolling interests		76	1
Ending Balance	$ 27,500	$ 17,654	$ 20,583