Securities - Net Securities Gains (Losses) (Details) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
Jun. 30, 2020	Mar. 31, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Securities [Abstract]
Realized gross gains	$ 16	$ 12	$ 12	$ 28	$ 17
Realized gross losses	(7)	(3)	(5)	(10)	(9)
Recognized gross impairments	0	0	0	0	0
Total net securities gains	$ 9	$ 9	$ 7	$ 18	$ 8

Securities [Abstract]

No definition available.

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- Definition

Amount of realized gain on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 9
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=121645371&loc=d3e27357-111563

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- Definition

Amount of realized gain (loss) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 9
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=121645371&loc=d3e27357-111563

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- Definition

Amount of realized loss on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

+ References

+ Details

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- Definition

Amount of other-than-temporary impairment (OTTI) on investment in debt security, recognized in earnings.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 45
-Paragraph 8A
-URI http://asc.fasb.org/extlink&oid=121553693&loc=SL6284422-111562

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