Accumulated other comprehensive income (loss) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Jun. 30, 2021	Dec. 31, 2020	Jun. 30, 2020	Dec. 31, 2019
Accumulated Other Comprehensive Income (Loss)
Accumulated Other Comprehensive Income (Loss), Foreign Currency Translation Adjustment	$ (1,400)	$ (1,381)	$ (1,400)	$ (1,381)
Gains (losses) on foreign currency translation	(230)	270	(461)	64
Less: Tax provision /(benefit)	12	(21)	29	(20)
Net gains (losses) on foreign currency translation	(242)	291	(490)	84
(Gains) losses reclassified to earnings	0	0	0	22
Less: Tax provision /(benefit)	0	0	0	0
Net (gains) losses reclassified to earnings	0	0	0	22
Other comprehensive income (loss), net of tax	(242)	291	(490)	106
Accumulated Other Comprehensive (Income) Loss, Pension and other postretirement benefits	(55)	(23)	(55)	(23)
Current year prior service credit (cost)	0	(2)	0	0
Pension and other postretirement benefits, Current year prior service credit (cost), tax (provision)/benefit	0	(1)	0	(1)
Net current year prior service credit (cost)	0	(1)	0	1
Amortization of prior service credit (cost)	(11)	(9)	(31)	(28)
Less: Tax provision /(benefit)	(3)	(2)	(8)	(7)
Net amortization of prior service (credit) cost	(8)	(7)	(23)	(21)
Pension and other post retirement benefits	(8)	(8)	(23)	(20)
AOCI, Cash Flow Hedge, Cumulative Gain (Loss), after Tax	(19)	(93)	(19)	(93)
Amount of gains (losses) recognized in AOCI	45	5	141	(93)
Other Comprehensive Income (Loss), Cash Flow Hedge, Gain (Loss), before Reclassification, Tax	3	2	22	(21)
Gains (losses) deferred, net of tax	42	3	119	(72)
Amount of gain (losses) reclassified from AOCI	(85)	93	(164)	98
Other Comprehensive Income (Loss), Cash Flow Hedge, Gain (Loss), Reclassification, Tax	(12)	20	(26)	22
Net (gains) losses reclassified to earnings	(73)	73	(138)	76
Other comprehensive income (loss), net of tax	(31)	76	(19)	4
AOCI, Debt Securities, Available-for-sale securities	34	49	34	49
Gains (losses) deferred	(4)	8	(22)	38
Less: Tax provision /(benefit)	0	0	(4)	9
Net gains (losses) deferred	(4)	8	(18)	29
(Gains) losses reclassified to earnings	(1)	0	(3)	0
Available-for-sale securities, (Gains) losses reclassified to earnings, tax (provision)/benefit	0	0	(1)	0
Net (gains) losses reclassified to earnings	(1)	0	(2)	0
Other comprehensive income (loss), net of tax	(5)	8	(20)	29
Accumulated other comprehensive income (loss)	$ (1,440)	$ (1,448)	$ (1,440)	$ (1,448)		$ (888)
Adjusted beginning balance
Accumulated Other Comprehensive Income (Loss)
Accumulated Other Comprehensive Income (Loss), Foreign Currency Translation Adjustment					$ (1,158)	(910)	$ (1,672)	$ (1,487)
Accumulated Other Comprehensive (Income) Loss, Pension and other postretirement benefits					(47)	(32)	(15)	(3)
AOCI, Cash Flow Hedge, Cumulative Gain (Loss), after Tax					12	0	(169)	(97)
AOCI, Debt Securities, Available-for-sale securities					$ 39	$ 54	$ 41	$ 20