Financial Instruments - Recurring fair value measurements (Details) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Assets
Derivatives	$ 74	$ 150
Investment securities	327
Assets, fair value	74	150
Liabilities
Derivatives	(82)	(95)
Total liabilities	(82)	(95)
Fair value, measurements, recurring
Assets
Derivatives	74	150
Investment securities	327	393
Assets, fair value	401	543
Liabilities
Derivatives	(82)	(95)
Total liabilities	(82)	(95)
Fair value, measurements, recurring \| Level 1
Assets
Derivatives	0	0
Investment securities	39	81
Assets, fair value	39	81
Liabilities
Derivatives	0	0
Total liabilities	0	0
Fair value, measurements, recurring \| Level 2
Assets
Derivatives	74	150
Investment securities	0	8
Assets, fair value	74	158
Liabilities
Derivatives	(82)	(95)
Total liabilities	(82)	(95)
Fair value, measurements, recurring \| Level 3
Assets
Derivatives	0	0
Investment securities	288	304
Assets, fair value	288	304
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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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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-Publisher FASB
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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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