Investments (Narrative) (Details) $ in Millions	Sep. 30, 2020 USD ($) security	Dec. 31, 2019 USD ($) security
Debt and Equity Securities, FV-NI [Line Items]
Accrued interest receivable	$ 197	$ 164
Number of HTM investment securities in an unrealized loss position \| security	68	146
Number of AFS investment securities in an unrealized loss position \| security	587	849
Allowance for credit loss on HTM securities	$ 1
Carrying value of pledged securities	2,200	$ 2,000
Securities Investment
Debt and Equity Securities, FV-NI [Line Items]
Accrued interest receivable	$ 51	$ 58

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.

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