Condensed Financial Information - Statements of Earnings and Comprehensive Income (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended																12 Months Ended
	Dec. 31, 2012		Sep. 30, 2012		Jun. 30, 2012		Mar. 31, 2012		Dec. 31, 2011		Sep. 30, 2011		Jun. 30, 2011		Mar. 31, 2011		Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
From consolidated subsidiaries:
Total revenues	$ 44,720		$ 41,050		$ 38,546		$ 38,147		$ 37,955		$ 33,739		$ 38,274		$ 33,720		$ 162,463	$ 143,688	$ 136,185
Cost and expense items:
Income taxes																	6,924	4,568	5,607
Total costs and expenses																	140,227	128,374	117,134
Net earnings attributable to Berkshire Hathaway shareholders	4,551	[1]	3,920	[1]	3,108	[1]	3,245	[1]	3,048	[1]	2,278	[1]	3,417	[1]	1,511	[1]	14,824	10,254	12,967
Comprehensive income attributable to Berkshire Hathaway shareholders																	24,670	7,249	15,756
Berkshire Hathaway (Parent) [Member]
From consolidated subsidiaries:
Dividends and distributions																	6,799	5,883	4,493
Undistributed earnings																	8,301	4,546	8,546
Total income from consolidated subsidiaries																	15,100	10,429	13,039
Other income																	88	101	115
Total revenues																	15,188	10,530	13,154
Cost and expense items:
General and administrative																	129	61	34
Interest to affiliates, net																	4	5	6
Other interest																	196	146	130
Income taxes																	35	64	17
Total costs and expenses																	364	276	187
Net earnings attributable to Berkshire Hathaway shareholders																	14,824	10,254	12,967
Other comprehensive income attributable to Berkshire Hathaway shareholders																	9,846	(3,005)	2,789
Comprehensive income attributable to Berkshire Hathaway shareholders																	$ 24,670	$ 7,249	$ 15,756

[1] Includes realized investment gains/losses, other-than-temporary impairment losses on investments and derivative gains/losses. Derivative gains/losses include significant amounts related to non-cash changes in the fair value of long-term contracts arising from short-term changes in equity prices, interest rates and foreign currency rates, among other factors. After-tax investment and derivative gains/losses for the periods presented above are as follows (in millions): 1st Quarter 2nd Quarter 3rd Quarter 4th Quarter Investment and derivative gains/losses - 2012 $ 580 $ (612 ) $ 521 $ 1,738 Investment and derivative gains/losses - 2011 (82 ) 713 (1,534 ) 382