Common stock - Narrative (Detail) (USD $)		0 Months Ended	9 Months Ended		0 Months Ended	9 Months Ended		0 Months Ended
	Sep. 30, 2014	Jun. 30, 2014 WPLG Inc. [Member] Graham Holding Company [Member]	Sep. 30, 2014 Common Stock Repurchase Program [Member]	Sep. 30, 2014 Class B [Member] Vote	Jun. 30, 2014 Class B [Member] WPLG Inc. [Member]	Sep. 30, 2014 Class A [Member] Vote	Dec. 31, 2013 Class A [Member]	Jun. 30, 2014 Class A [Member] WPLG Inc. [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						1,642,814	1,643,954
Preferred Stock, shares authorized	1,000,000
Preferred Stock, shares issued	0
Preferred Stock, shares outstanding	0
Shares repurchase, authorization description			Berkshire's Board of Directors ("Berkshire's Board") has approved a common stock repurchase program under which Berkshire may repurchase its Class A and Class B shares at prices no higher than a 20% premium over the book value of the shares.
Minimum cash equivalent threshold after repurchase of common stock shares, amount			$ 20,000,000,000
Number of shares acquired			0	1,278	1,278	2,107		2,107
Number of shares exchanged		1,620,190