Investments (Narrative) (Details) $ in Millions	Mar. 31, 2023 USD ($) security	Dec. 31, 2022 USD ($) security
Debt and Equity Securities, FV-NI [Line Items]
Transfer from available for sale to held-to-maturity, amortized cost		$ 13,100
Transfer from available for sale to held-to-maturity, fair value		10,700
Amortized basis of held-to-maturity securities		2,400
Amortized basis of held-to-maturity securities, after tax		$ 1,800
Number of AFS investment securities in an unrealized loss position | security	3,240	3,562
Allowance for credit loss on HTM securities (less than)	$ 1
Available-for-sale, at fair value	11,594	$ 11,915
Securities Investment
Debt and Equity Securities, FV-NI [Line Items]
Accrued interest receivable	$ 65	$ 75