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Investment Securities (Narrative) (Details) $ in Millions		12 Months Ended
		Dec. 31, 2019 USD ($)	Dec. 31, 2021 USD ($)	Dec. 31, 2020 USD ($)
Debt Securities, Available-for-sale, Unrealized Loss Position, Number of Positions			461
Loan interest receivable			$ 23	$ 18
Repositioning lower-yielding treasury securities		$ 1,000
Investment securities available-for-sale, Amortized Cost			17,116	14,752
Investment Securities, Available-for-sale			16,986	15,028
Carrying value of securities pledged			2,700
Pledged to the FHLB as collateral for potential future borrowings			1,700
Debt Instrument, Unused Borrowing Capacity, Amount			1,600
Securities Borrowed, Liability			1,000
Liabilities secured by pledged collateral			$ 946
U.S. Treasury and other U.S. government agency securities
Debt Securities, Available-for-sale, Unrealized Loss Position, Number of Positions			20
Investment securities available-for-sale, Amortized Cost			$ 3,010	4,583
Investment Securities, Available-for-sale			$ 2,993	4,658
Residential mortgage-backed securities
Debt Securities, Available-for-sale, Unrealized Loss Position, Number of Positions			406
Debt Securities			$ 13,300
Investment securities available-for-sale, Amortized Cost	[1]		13,397	10,169
Investment Securities, Available-for-sale	[1]		13,288	$ 10,370
Residential mortgage-backed securities | Prepayment options
Debt Securities			$ 13,400
Commercial Mortgage Backed Securities
Debt Securities, Available-for-sale, Unrealized Loss Position, Number of Positions			35
Investment securities available-for-sale, Amortized Cost	[1]		$ 709
Investment Securities, Available-for-sale	[1]		$ 705
[1] Issued and/or guaranteed by U.S. government agencies or U.S. government-sponsored enterprises.

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