Accumulated other comprehensive income - Reclassified Amounts (Detail) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Investment gains/losses	$ 362	$ 2,366	$ 459	$ 3,497
Reclassifications before income taxes	5,846	8,916	13,493	15,514
Applicable income taxes	1,739	2,458	4,153	4,283
Total amounts reclassified from other comprehensive income into net earnings	4,107	6,458	9,340	11,231
Insurance and Other [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Investment gains/losses	136	$ 2,366	232	3,425
Finance and Financial Products [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Investment gains/losses	$ 226		227	72
Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Other			24	38
Reclassifications before income taxes			(171)	(3,411)
Applicable income taxes			(55)	(1,216)
Total amounts reclassified from other comprehensive income into net earnings			(116)	(2,195)
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			(194)	(3,377)
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			(1)	(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			(195)	(3,449)
Applicable income taxes			(68)	(1,207)
Total amounts reclassified from other comprehensive income into net earnings			(127)	(2,242)
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			(194)	(3,377)
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			(1)	(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				47
Total amounts reclassified from other comprehensive income into net earnings				47
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			15	36
Reclassifications before income taxes			15	36
Applicable income taxes			7	9
Total amounts reclassified from other comprehensive income into net earnings			8	27
Other AOCI transactions [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Other			9	(45)
Reclassifications before income taxes			9	(45)
Applicable income taxes			6	(18)
Total amounts reclassified from other comprehensive income into net earnings			$ 3	$ (27)