Supplemental financial information - Amounts reclassified out of AOCI (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2015		Mar. 31, 2014
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Line Items]
Provision for income taxes	$ 284		$ 184
Net income	(656)		(487)
Reclassification out of Accumulated Other Comprehensive Income | 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	14	[1],[2]	15	[1],[2]
Provision for income taxes	(4)		(5)
Net income	10		10
Reclassification out of Accumulated Other Comprehensive Income | Accumulated Defined Benefit Plans Adjustment, Net Prior Service Cost (Credit)
Reclassification Adjustment Out Of Accumulated Other Comprehensive Income [Line Items]
Prior service cost of defined benefit plans:	1	[1],[2]	0	[1],[2]
Provision for income taxes	0		0
Net income	$ 1		$ 0

[1] Detailed in Note 8.

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