Accumulated other comprehensive income (loss) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020	Mar. 31, 2021	Dec. 31, 2020	Mar. 31, 2020	Dec. 31, 2019
Accumulated Other Comprehensive Income (Loss)
Accumulated Other Comprehensive Income (Loss), Foreign Currency Translation Adjustment	$ (1,158)	$ (1,672)	$ (1,158)	$ (1,672)
Gains (losses) on foreign currency translation	92	168	(231)	(206)
Less: Tax provision /(benefit)	(7)	(9)	17	1
Net gains (losses) on foreign currency translation	99	177	(248)	(207)
(Gains) losses reclassified to earnings	0	(2)	0	22
Less: Tax provision /(benefit)	0	0	0	0
Net (gains) losses reclassified to earnings	0	(2)	0	22
Other comprehensive income (loss), net of tax	99	175	(248)	(185)
Accumulated Other Comprehensive (Income) Loss, Pension and other postretirement benefits	(47)	(15)	(47)	(15)
Current year prior service credit (cost)	0	2	0	2
Pension and other postretirement benefits, Current year prior service credit (cost), tax (provision)/benefit	0	0	0	0
Net current year prior service credit (cost)	0	2	0	2
Amortization of prior service credit (cost)	(10)	(10)	(20)	(19)
Less: Tax provision /(benefit)	(3)	(3)	(5)	(5)
Net amortization of prior service (credit) cost	(7)	(7)	(15)	(14)
Pension and other post retirement benefits	(7)	(5)	(15)	(12)
AOCI, Cash Flow Hedge, Cumulative Gain (Loss), after Tax	12	(169)	12	(169)
Amount of gains (losses) recognized in AOCI	17	(90)	96	(98)
Other Comprehensive Income (Loss), Cash Flow Hedge, Gain (Loss), before Reclassification, Tax	3	(20)	19	(23)
Gains (losses) deferred, net of tax	14	(70)	77	(75)
Amount of gain (losses) reclassified from AOCI	39	75	(79)	5
Other Comprehensive Income (Loss), Cash Flow Hedge, Gain (Loss), Reclassification, Tax	10	17	(14)	2
Net (gains) losses reclassified to earnings	29	58	(65)	3
Other comprehensive income (loss), net of tax	43	(12)	12	(72)
AOCI, Debt Securities, Available-for-sale securities	39	41	39	41
Gains (losses) deferred	3	52	(18)	30
Less: Tax provision /(benefit)	1	13	(4)	9
Net gains (losses) deferred	2	39	(14)	21
(Gains) losses reclassified to earnings	(2)	0	(2)	0
Available-for-sale securities, (Gains) losses reclassified to earnings, tax (provision)/benefit	(1)	0	(1)	0
Net (gains) losses reclassified to earnings	(1)	0	(1)	0
Other comprehensive income (loss), net of tax	1	39	(15)	21
Accumulated other comprehensive income (loss)	$ (1,154)	$ (1,815)	$ (1,154)	$ (1,815)		$ (888)
Adjusted beginning balance
Accumulated Other Comprehensive Income (Loss)
Accumulated Other Comprehensive Income (Loss), Foreign Currency Translation Adjustment					$ (1,257)	(910)	$ (1,847)	$ (1,487)
Accumulated Other Comprehensive (Income) Loss, Pension and other postretirement benefits					(40)	(32)	(10)	(3)
AOCI, Cash Flow Hedge, Cumulative Gain (Loss), after Tax					(31)	0	(157)	(97)
AOCI, Debt Securities, Available-for-sale securities					$ 38	$ 54	$ 2	$ 20