Accumulated other comprehensive income - Reclassified Amounts (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Investment gains/losses	$ (376)	$ 1,714	$ 3,121	$ 2,711
Reclassifications before income taxes	6,750	7,378	22,264	21,564
Applicable income taxes	2,029	2,225	6,312	6,782
Total amounts reclassified from other comprehensive income into net earnings	4,721	5,153	15,952	14,782
Insurance and Other [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Investment gains/losses	(376)	1,640	3,049	2,529
Finance and Financial Products [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Investment gains/losses		74	72	182
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			59	91
Reclassifications before income taxes			(2,973)	(1,044)
Applicable income taxes			(1,064)	(360)
Total amounts reclassified from other comprehensive income into net earnings			(1,909)	(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			(2,960)	(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			(72)	(73)
Unrealized appreciation of investments, net [Member] | 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]
Reclassifications before income taxes			(3,032)	(1,135)
Applicable income taxes			(1,061)	(397)
Total amounts reclassified from other comprehensive income into net earnings			(1,971)	(738)
Unrealized appreciation of investments, net [Member] | 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			(2,960)	(1,062)
Unrealized appreciation of investments, net [Member] | 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			(72)	(73)
Foreign currency translation [Member] | 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			47	(31)
Reclassifications before income taxes			47	(31)
Total amounts reclassified from other comprehensive income into net earnings			47	(31)
Prior service and actuarial gains/losses of defined benefit pension plans [Member] | 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			51	114
Reclassifications before income taxes			51	114
Applicable income taxes			12	33
Total amounts reclassified from other comprehensive income into net earnings			39	81
Other AOCI transactions [Member] | 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			(39)	8
Reclassifications before income taxes			(39)	8
Applicable income taxes			(15)	4
Total amounts reclassified from other comprehensive income into net earnings			$ (24)	$ 4