Investments (Gains and Losses, Including OTTI, Recognized In Statement of Income) (Details) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Investments [Abstract]
Other noninterest-bearing investments, Nonmarketable equity securities, Gross gains	$ 6	$ 5	$ 86	$ 13
Other noninterest-bearing investments, Nonmarketable equity securities, Gross losses	29	1	35	18
Net gains (losses)	$ (23)	$ 4	$ 51	$ (5)

Amount of realized and unrealized gain (loss) on investment.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
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Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
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-URI http://asc.fasb.org/extlink&oid=123367319&loc=SL114868664-224227

Reference 3: http://www.xbrl.org/2003/role/recommendedDisclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
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