Investments (Narrative) (Details) $ in Millions	Sep. 30, 2021 USD ($) security	Dec. 31, 2020 USD ($) security
Debt and Equity Securities, FV-NI [Line Items]
Accrued interest receivable	$ 175	$ 200
Number of HTM investment securities in an unrealized loss position \| security	122	119
Number of AFS investment securities in an unrealized loss position \| security	1,241	549
Allowance for credit loss on HTM securities (less than)	$ 1
Carrying value of pledged securities	2,400	$ 2,300
Securities Investment
Debt and Equity Securities, FV-NI [Line Items]
Accrued interest receivable	$ 57	$ 54

Number of investments in debt securities measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), in unrealized loss position, without allowance for credit loss. Includes beneficial interest in securitized financial asset.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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-Name Accounting Standards Codification
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Amount, excluding accrued interest, of allowance for credit loss on investment in debt security measured at amortized cost (held-to-maturity).

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Carrying amount as of the balance sheet date of interest earned but not received. Also called accrued interest or accrued interest receivable.

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