Accumulated other comprehensive income (loss) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Dec. 31, 2020	Dec. 31, 2019
Accumulated Other Comprehensive Income (Loss)
Accumulated Other Comprehensive Income (Loss), Foreign Currency Translation Adjustment	$ (1,257)	$ (1,847)	$ (910)	$ (1,487)
Gains (losses) on foreign currency translation	(323)	(374)
Less: Tax provision /(benefit)	24	10
Net gains (losses) on foreign currency translation	(347)	(384)
(Gains) losses reclassified to earnings	0	24
Less: Tax provision /(benefit)	0	0
Net (gains) losses reclassified to earnings	0	24
Other comprehensive income (loss), net of tax	(347)	(360)
Accumulated Other Comprehensive (Income) Loss, Pension and other postretirement benefits	(40)	(10)	(32)	(3)
Current year prior service credit (cost)	0	0
Pension and other postretirement benefits, Current year prior service credit (cost), tax (provision)/benefit	0	0
Net current year prior service credit (cost)	0	0
Amortization of prior service credit (cost)	(10)	(9)
Less: Tax provision /(benefit)	(2)	(2)
Net amortization of prior service (credit) cost	(8)	(7)
Pension and other post retirement benefits	(8)	(7)
AOCI, Cash Flow Hedge, Cumulative Gain (Loss), after Tax	(31)	(157)	0	(97)
Amount of gains (losses) recognized in AOCI	79	(8)
Other Comprehensive Income (Loss), Cash Flow Hedge, Gain (Loss), before Reclassification, Tax	16	(3)
Gains (losses) deferred, net of tax	63	(5)
Amount of gain (losses) reclassified from AOCI	(118)	(70)
Other Comprehensive Income (Loss), Cash Flow Hedge, Gain (Loss), Reclassification, Tax	(24)	(15)
Net (gains) losses reclassified to earnings	(94)	(55)
Other comprehensive income (loss), net of tax	(31)	(60)
AOCI, Debt Securities, Available-for-sale securities	38	2	54	$ 20
Gains (losses) deferred	(21)	(22)
Less: Tax provision /(benefit)	(5)	(4)
Net gains (losses) deferred	(16)	(18)
(Gains) losses reclassified to earnings	0	0
Available-for-sale securities, (Gains) losses reclassified to earnings, tax (provision)/benefit	0	0
Net (gains) losses reclassified to earnings	0	0
Other comprehensive income (loss), net of tax	(16)	(18)
Accumulated other comprehensive income (loss)	$ (1,290)	$ (2,012)	$ (888)