Accumulated other comprehensive income - Reclassified Amounts (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Investment gains/losses	$ 8,266	$ (376)	$ 8,725	$ 3,121
Reclassifications before income taxes	14,072	6,750	27,565	22,264
Applicable income taxes	4,545	2,029	8,698	6,312
Total amounts reclassified from other comprehensive income into net earnings	9,527	4,721	18,867	15,952
Insurance and Other [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Investment gains/losses	8,339	$ (376)	8,571	3,049
Finance and Financial Products [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Investment gains/losses	$ (73)		154	72
Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Other			20	59
Reclassifications before income taxes			(1,564)	(2,973)
Applicable income taxes			(546)	(1,064)
Total amounts reclassified from other comprehensive income into net earnings			(1,018)	(1,909)
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			(1,498)	(2,960)
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			(86)	(72)
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			(1,781)	(3,032)
Applicable income taxes			(623)	(1,061)
Total amounts reclassified from other comprehensive income into net earnings			(1,158)	(1,971)
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			(1,695)	(2,960)
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			(86)	(72)
Foreign currency translation [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Other				47
Reclassifications before income taxes			197	47
Applicable income taxes			69
Total amounts reclassified from other comprehensive income into net earnings			128	47
Foreign currency translation [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			197
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			2	51
Reclassifications before income taxes			2	51
Applicable income taxes			1	12
Total amounts reclassified from other comprehensive income into net earnings			1	39
Other AOCI transactions [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Other			18	(39)
Reclassifications before income taxes			18	(39)
Applicable income taxes			7	(15)
Total amounts reclassified from other comprehensive income into net earnings			$ 11	$ (24)