Investment Securities (Investment Income) (Details) - USD ($) $ in Millions	3 Months Ended
Mar. 31, 2021	Mar. 31, 2020
Taxable interest	$ 114	$ 205
Taxable dividends	5	5
Interest and dividends exempt from U.S. federal income tax	5	3
Interest and dividends on investment securities and other earning assets	131	226
Excludes other earning assets
Interest and dividends on investment securities and other earning assets	$ 124	$ 213

Amount of operating dividend income on securities.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 220
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-04.2)
-URI http://asc.fasb.org/extlink&oid=120399700&loc=SL114874048-224260

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Amount of operating dividend and interest income, including amortization and accretion of premiums and discounts, on securities.

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Interest income, including any amortization and accretion (as applicable) of discounts and premiums, derived from debt securities issued by municipal governments, local taxing districts and US state government agencies.

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Amount of operating interest income, including amortization and accretion of premiums and discounts, on securities subject to state, federal and other income tax.

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