Supplemental financial information - Amounts reclassified out of AOCI (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014		Dec. 31, 2013		Dec. 31, 2012
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Net actuarial gains (losses) of defined benefit plans									$ (63)
Prior service cost of defined benefit plans									0
Interest and debt expense									94		95		85
Provision for income taxes									1,053		592		176
Net income	(825)	(826)	(683)	(487)	(511)	(629)	(660)	(362)	(2,821)		(2,162)		(1,759)
Reclassification out of Accumulated Other Comprehensive Income [Member] | Accumulated Defined Benefit Plans Adjustment, Net Unamortized Gain (Loss) [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Net actuarial gains (losses) of defined benefit plans									63	[1],[2]	108	[1],[2]
Provision for income taxes									(21)		(37)
Net income									42		71
Reclassification out of Accumulated Other Comprehensive Income [Member] | Accumulated Defined Benefit Plans Adjustment, Net Prior Service Cost (Credit) [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Prior service cost of defined benefit plans									0	[1],[2]	(5)	[1],[2]
Provision for income taxes									0		2
Net income									0		(3)
Reclassification out of Accumulated Other Comprehensive Income [Member] | Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Interest and debt expense									2		2
Provision for income taxes									(1)		(1)
Net income									$ 1		$ 1

[1] Pension expense is included in COR, R&D, SG&A and Restructuring charges/other in the Consolidated Statements of Income.

[2] Detailed in Note 11.