Financial Instruments - Cumulative Basis Adjustments for Fair Value Hedges (Details) - USD ($) $ in Millions	Jun. 30, 2019	Dec. 31, 2018
Short-term debt
Amounts recorded in the Consolidated Statement of Financial Position related to cumulative basis adjustments for fair value hedges
Carrying amount of the hedged item	$ (1,128)	$ (1,878)
Cumulative hedging adjustment included in the carrying amount - assets/(liabilities)	(3)	(4)
Hedging adjustments on discontinued hedging relationships	(2)	(6)
Long-term debt
Amounts recorded in the Consolidated Statement of Financial Position related to cumulative basis adjustments for fair value hedges
Carrying amount of the hedged item	(4,826)	(6,004)
Cumulative hedging adjustment included in the carrying amount - assets/(liabilities)	(461)	(333)
Hedging adjustments on discontinued hedging relationships	$ (388)	$ (213)

Amount of cumulative increase (decrease) in fair value of hedged liability in fair value hedge, attributable to hedged risk, remaining after discontinued hedge.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4EE
-Subparagraph (d)
-URI http://asc.fasb.org/extlink&oid=109980867&loc=SL109999712-113959

+ Details

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Balance Type:	credit
Period Type:	instant

- Definition

Amount of liability hedged in fair value hedging relationship.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4EE
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=109980867&loc=SL109999712-113959

+ Details

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Balance Type:	credit
Period Type:	instant

- Definition

Amount of cumulative increase (decrease) in fair value of hedged liability in fair value hedge, attributable to hedged risk.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4EE
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=109980867&loc=SL109999712-113959

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- References

No definition available.

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