Investment Securities - Gains and Losses Related to Investment Securities (Details) (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Investments, Debt and Equity Securities [Abstract]
Gross realized gains from sales of AFS investment securities	$ 31	$ 205	$ 74
Gross realized losses from sales of AFS investment securities	(32)	(196)	(113)
Gross losses from OTTI	0	(3)	0
Gains (losses) related to investment securities, net	(1)	6	(39)
Impairment associated with adverse changes in timing of expected future cash flows	0	(3)	0
Net impairment losses	$ 0	$ (3)	$ 0

Impairment Associated With Adverse Changes In Timing Of Expected Future Cash Flows

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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=118939692&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

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- Definition

The amount by which the fair value of an investment is less than the amortized cost basis or carrying amount of that investment at the balance sheet date and the decline in fair value is deemed to be other than temporary, before considering whether or not such amount is recognized in earnings or other comprehensive income.

+ 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=118954083&loc=SL6284422-111562

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- References

No definition available.

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- Definition

Amount of unrealized and realized gain (loss) on investment in marketable security, including other-than-temporary impairment (OTTI).

+ References

No definition available.

+ Details

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- Definition

Amount of unrealized and realized gain (loss) on investment in marketable security, excluding other-than-temporary impairment (OTTI).

+ References

No definition available.

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