Derivative Financial Instruments - Change in the Fair Value for Interest Rate Contracts and the Related Hedged Items (Details) - Fair Value Hedging - USD ($) $ in Millions	3 Months Ended	6 Months Ended
Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020	Dec. 31, 2020
Long-term debt
Derivatives, Fair Value
Carrying amount of the hedged items	$ 1,879		$ 1,879		$ 2,478
Cumulative amount of fair value hedging adjustments included in the carrying amount of the hedged items	435		435		$ 534
Interest rate contracts \| Interest on long-term debt
Derivatives, Fair Value
Change in fair value of interest rate swaps hedging long- term debt	46	$ (1)	(99)	$ 226
Change in fair value of hedged long-term debt attributable to the risk being hedged	$ (46)	$ 2	$ 99	$ (225)

Carrying amount of hedged item.

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- Definition

Cumulative amount of fair value hedging adjustments.

+ References

No definition available.

+ Details

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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

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- Definition

Amount of unrealized gain (loss) included in earnings related to the fair value of the hedged item in an interest rate fair value hedge, offset by the gain (loss) on the hedging instrument to the extent that the fair value hedge is determined to be effective.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4A
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=125515794&loc=SL5618551-113959

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4C
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=125515794&loc=SL5624171-113959

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- Definition

Amount of unrealized gain (loss) related to the fair value of interest rate derivatives designated as fair value hedging instruments, as offset by the gain (loss) on the hedged item to the extent that the fair value hedge is determined to be effective.

+ References

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