Financial Instruments - Recurring fair value measurements (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Assets
Derivatives	$ 118	$ 58
Investment securities	1,532	283
Liabilities
Derivatives	(52)	(27)
Debt and Equity Securities, Unrealized Gain (Loss)	1,400	2	$ (25)
Fair value, measurements, recurring
Assets
Derivatives	118	58
Investment securities	1,532	283
Assets, fair value	1,650	341
Liabilities
Derivatives	(52)	(27)
Total liabilities	(52)	(27)
Fair value, measurements, recurring \| Level 1
Assets
Derivatives	0	0
Investment securities	1,502	24
Assets, fair value	1,502	24
Liabilities
Derivatives	0	0
Total liabilities	0	0
Fair value, measurements, recurring \| Level 2
Assets
Derivatives	118	58
Investment securities	0	0
Assets, fair value	118	58
Liabilities
Derivatives	(52)	(27)
Total liabilities	(52)	(27)
Fair value, measurements, recurring \| Level 3
Assets
Derivatives	0	0
Investment securities	30	259
Assets, fair value	30	259
Liabilities
Derivatives	0	0
Total liabilities	$ 0	$ 0

Fair value portion of probable future economic benefits obtained or controlled by an entity as a result of past transactions or events.

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Amount of unrealized gain (loss) on investment in debt and equity securities.

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Fair value, after the effects of master netting arrangements, of a financial asset or other contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset. Includes assets not subject to a master netting arrangement and not elected to be offset.

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Fair value, after the effects of master netting arrangements, of a financial liability or contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset. Includes liabilities not subject to a master netting arrangement and not elected to be offset.

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Fair value portion of investment securities, including, but not limited to, marketable securities, derivative financial instruments, and investments accounted for under the equity method.

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Fair value of financial and nonfinancial obligations.

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