Derivative Instruments and Hedging Activities (Gain (Loss) Recorded in Income) (Details) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Derivative Instruments, Gain (Loss) [Line Items]
Total income statement impact	$ 2	$ 8	$ 15	$ (15)
Interest rate swaps
Derivative Instruments, Gain (Loss) [Line Items]
Derivatives	(4)	(3)	(27)	72
Hedged items	4	3	27	(72)
Total income statement impact	0	0	0	0
Asset hedges: Pay-fixed interest rate swaps
Derivative Instruments, Gain (Loss) [Line Items]
Derivatives	4	11	27	11
Hedged items	(4)	(11)	(27)	(11)
Total income statement impact	$ 0	$ 0	$ 0	$ 0

Amount of increase (decrease) in the fair value of derivatives recognized in the income statement.

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4A
-Subparagraph (b)(1)
-URI http://asc.fasb.org/extlink&oid=125515794&loc=SL5618551-113959

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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

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
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-Section 50
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-URI http://asc.fasb.org/extlink&oid=125515794&loc=SL5624171-113959

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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.

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