Accumulated other comprehensive income - Reclassified Amounts (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013		Sep. 30, 2012
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Investment gains/losses	$ 1,714	$ 917	$ 2,711		$ 936
Reclassifications before income taxes	7,378	5,936	21,564		15,482
Applicable income taxes	2,225	1,882	6,782		4,831
Total amounts reclassified from other comprehensive income into net earnings	5,153	4,054	14,782		10,651
Insurance and Other [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Investment gains/losses	1,640	725	2,529		720
Finance and Financial Products [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Investment gains/losses	74	192	182		216
Portion Attributable to Berkshire Hathaway Shareholders [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Other			91	[1]
Reclassifications before income taxes			(1,044)
Applicable income taxes			(360)
Total amounts reclassified from other comprehensive income into net earnings			(684)
Portion Attributable to Berkshire Hathaway Shareholders [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member] | Insurance and Other [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Investment gains/losses			(1,062)
Portion Attributable to Berkshire Hathaway Shareholders [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member] | Finance and Financial Products [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Investment gains/losses			(73)
Portion Attributable to Berkshire Hathaway Shareholders [Member] | Unrealized appreciation of investments, net [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Reclassifications before income taxes			(1,135)
Applicable income taxes			(397)
Total amounts reclassified from other comprehensive income into net earnings			(738)
Portion Attributable to Berkshire Hathaway Shareholders [Member] | Unrealized appreciation of investments, net [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member] | Insurance and Other [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Investment gains/losses			(1,062)
Portion Attributable to Berkshire Hathaway Shareholders [Member] | Unrealized appreciation of investments, net [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member] | Finance and Financial Products [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Investment gains/losses			(73)
Portion Attributable to Berkshire Hathaway Shareholders [Member] | Foreign currency translation [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Other			(31)	[1]
Reclassifications before income taxes			(31)
Total amounts reclassified from other comprehensive income into net earnings			(31)
Portion Attributable to Berkshire Hathaway Shareholders [Member] | Prior service and actuarial gains/losses of defined benefit pension plans [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Other			114	[1]
Reclassifications before income taxes			114
Applicable income taxes			33
Total amounts reclassified from other comprehensive income into net earnings			81
Portion Attributable to Berkshire Hathaway Shareholders [Member] | Other AOCI transactions [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Other			8	[1]
Reclassifications before income taxes			8
Applicable income taxes			4
Total amounts reclassified from other comprehensive income into net earnings			$ 4

[1] Amounts are included on various line items, and are immaterial individually and in the aggregate.