Accumulated other comprehensive income - Reclassified Amounts (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Investment gains/losses	$ 9,373	$ 3,575	$ 4,065
Reclassifications before income taxes	34,946	28,105	28,796
Applicable income taxes	10,532	7,935	8,951
Total amounts reclassified from other comprehensive income into net earnings	24,414	20,170	19,845
Insurance and Other [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Investment gains/losses	9,363	3,503	3,881
Finance and Financial Products [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Investment gains/losses	10	72	184
Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Other	164	94	153
Reclassifications before income taxes	(1,971)	(3,266)	(2,294)
Applicable income taxes	(691)	(1,171)	(796)
Total amounts reclassified from other comprehensive income into net earnings	(1,280)	(2,095)	(1,498)
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	(2,194)	(3,288)	(2,382)
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	59	(72)	(65)
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	(2,332)	(3,360)	(2,447)
Applicable income taxes	(816)	(1,176)	(856)
Total amounts reclassified from other comprehensive income into net earnings	(1,516)	(2,184)	(1,591)
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	(2,391)	(3,288)	(2,382)
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	59	(72)	(65)
Foreign currency translation [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Other		75	(31)
Reclassifications before income taxes	197	75	(31)
Applicable income taxes	69	9
Total amounts reclassified from other comprehensive income into net earnings	128	66	(31)
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	129	58	167
Reclassifications before income taxes	129	58	167
Applicable income taxes	43	13	53
Total amounts reclassified from other comprehensive income into net earnings	86	45	114
Other AOCI transactions [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Other	35	(39)	17
Reclassifications before income taxes	35	(39)	17
Applicable income taxes	13	(17)	7
Total amounts reclassified from other comprehensive income into net earnings	$ 22	$ (22)	$ 10