Supplemental financial information - Amounts Reclassified out of AOCI (Details) - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2020	Mar. 31, 2019
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Other income (expense), net (OI&E)		$ 25	$ 36
Provision for income taxes		(50)	(160)
Net income		1,174	1,217
Reclassification out of Accumulated Other Comprehensive Income | Net actuarial losses of defined benefit plans
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Other income (expense), net (OI&E)	[1]	10	13
Provision for income taxes		(2)	(3)
Net income		$ 8	$ 10

[1] Detailed in Note 6.