Supplemental financial information - Amounts Reclassified out of AOCI (Details) - USD ($) $ in Millions		3 Months Ended								12 Months Ended
		Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Line Items]
Net actuarial gains (losses) of defined benefit plans										$ 78
Provision for income taxes										1,230	$ 1,053	$ 592
Net income		$ (836)	$ (798)	$ (696)	$ (656)	$ (825)	$ (826)	$ (683)	$ (487)	(2,986)	(2,821)	(2,162)
Prior service (cost) credit of defined benefit plans										0
Interest and debt expense										90	94	95
Reclassification out of Accumulated Other Comprehensive Income | Accumulated Defined Benefit Plans Adjustment, Net Unamortized Gain (Loss)
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Line Items]
Net actuarial gains (losses) of defined benefit plans	[1],[2]									78	63	108
Provision for income taxes										(25)	(21)	(37)
Net income										53	42	71
Reclassification out of Accumulated Other Comprehensive Income | Accumulated Defined Benefit Plans Adjustment, Net Prior Service Cost (Credit) and Curtailment Gain
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Line Items]
Provision for income taxes										0	0	2
Net income										0	0	(3)
Prior service (cost) credit of defined benefit plans	[1],[2]									0	0	(5)
Reclassification out of Accumulated Other Comprehensive Income | Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Line Items]
Provision for income taxes										(1)	(1)	(1)
Net income										1	1	1
Interest and debt expense										$ 2	$ 2	$ 2

[1] Detailed in Note 10.

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