Quarterly data (Detail) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended																12 Months Ended
	Dec. 31, 2016		Sep. 30, 2016		Jun. 30, 2016		Mar. 31, 2016		Dec. 31, 2015		Sep. 30, 2015		Jun. 30, 2015		Mar. 31, 2015		Dec. 31, 2016		Dec. 31, 2015		Dec. 31, 2014
Quarterly Financial Information [Line Items]
Revenues	$ 58,344		$ 58,843		$ 54,254		$ 52,163		$ 51,731		$ 59,070		$ 51,549		$ 48,593		$ 223,604		$ 210,943		$ 194,699
Net earnings attributable to Berkshire shareholders	6,286	[1]	7,198	[1]	5,001	[1]	5,589	[1]	5,478	[1]	9,428	[1]	4,013	[1]	5,164	[1]	$ 24,074		$ 24,083		$ 19,872
Investment and derivative gains/losses	$ 1,904		$ 2,347		$ 394		$ 1,852		$ 805		$ 4,877		$ 123		$ 920
Class A [Member]
Quarterly Financial Information [Line Items]
Net earnings attributable to Berkshire shareholders per equivalent Class A common share	$ 3,823		$ 4,379		$ 3,042		$ 3,401		$ 3,333		$ 5,737		$ 2,442		$ 3,143		$ 14,645	[2]	$ 14,656	[2]	$ 12,092	[2]

[1] Includes investment and derivative gains/losses. 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-2016 $ 1,852 $ 394 $ 2,347 $ 1,904 Investment and derivative gains/losses-2015 920 123 4,877 805

[2] Equivalent Class B shares outstanding are 1,500 times the equivalent Class A amount. Net earnings per equivalent Class B share outstanding are one-fifteen-hundredth of the equivalent Class A amount or $9.76 for 2016, $9.77 for 2015 and $8.06 for 2014.