Common stock - Narrative (Detail) (USD $)	3 Months Ended				3 Months Ended
	Mar. 31, 2014 Class B [Member] Vote	Mar. 31, 2014 Class A [Member] Vote	Dec. 31, 2013 Class A [Member]	Mar. 31, 2014 Preferred Stock [Member]	Mar. 31, 2014 Common Stock [Member]
Class of Stock [Line Items]
Ratio of net earnings per equivalent common share and dividend and distribution rights of Class B shares to Class A shares	0.000667
Number of votes entitled per share, number	0.0001	1
Number of shares of Class B stock obtainable from converting one Class A share	1,500
Class A equivalent shares outstanding		1,644,289	1,643,954
Preferred Stock, shares authorized				1,000,000
Preferred Stock, shares issued				0
Preferred Stock, shares outstanding				0
Shares repurchase, authorization description					In September 2011, Berkshire's Board of Directors ("Berkshire's Board") approved a common stock repurchase program under which Berkshire may repurchase its Class A and Class B shares at prices no higher than a 10% premium over the book value of the shares. In December 2012, Berkshire's Board amended the repurchase program by raising the price limit to no higher than a 20% premium over book value.
Minimum cash equivalent threshold after repurchase of common stock shares, amount					$ 20,000,000,000