Stockholders' equity (Components of AOCI) (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning Balance	$ 9,409	$ 9,673	$ 12,500
Foreign currency translation adjustments	(135)	9	(48)
Ending Balance	6,700	9,409	9,673
Cumulative effect of changes in accounting principles, net of taxes
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning Balance		(2)
Ending Balance			(2)
Foreign currency translation [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning Balance	(709)	(718)	(670)
Foreign currency translation adjustments	(135)	9	(48)
Income taxes	0	0	0
Ending Balance	(844)	(709)	(718)
Cash flow hedges [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning Balance	(263)	175	241
Unrealized gains (losses)	159	(61)	127
Reclassification adjustments to income	(253)	501	(211)
Income taxes	(88)	124	18
Ending Balance	61	(263)	175
Available-for-sale securities [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning Balance	1	22	(338)
Unrealized gains (losses)	(1)	6	424
Reclassification adjustments to income	0	33	(56)
Income taxes	0	6	(8)
Ending Balance	0	1	22
Other [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning Balance	(14)	(7)	(2)
Other gains	1	(7)	(5)
Ending Balance	(13)	(14)	(7)
AOCI [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning Balance	(985)	(528)	(769)
Foreign currency translation adjustments	(135)	9	(48)
Unrealized gains (losses)	158	(55)	551
Reclassification adjustments to income	253	(534)	(267)
Other gains	1	(7)	(5)
Income taxes	(88)	130	10
Ending Balance	$ (796)	$ (985)	$ (528)

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Amount before tax and reclassification adjustments of other comprehensive income (loss) attributable to parent.

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Amount after tax and reclassification adjustments of gain (loss) on foreign currency translation adjustments, foreign currency transactions designated and effective as economic hedges of a net investment in a foreign entity and intra-entity foreign currency transactions that are of a long-term-investment nature, attributable to parent entity.

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Amount of tax expense (benefit) allocated to other comprehensive income (loss) attributable to parent entity.

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