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Investment Securities (Narrative) (Details) $ in Millions		3 Months Ended
		Jun. 30, 2022 USD ($)	Jun. 30, 2021 USD ($)	Dec. 31, 2021 USD ($)
Securities with no credit impairment in unrealized loss position		1,211
Loan interest receivable		$ 49		$ 36
Securities gains and losses		0	$ 0
Investment securities available-for-sale, Amortized Cost		22,785		17,116
Investment securities available-for-sale		20,829		16,986
Carrying value of securities pledged		2,800
Pledged to the FHLB as collateral for potential future borrowings		1,300
Collateral for potential future borrowings		1,600
Liabilities secured by pledged collateral		$ 977
U.S. Treasury and other U.S. government agency securities
Securities with no credit impairment in unrealized loss position		28
Investment securities available-for-sale, Amortized Cost		$ 2,925		3,010
Investment securities available-for-sale		$ 2,802		2,993
Residential Mortgage Backed Securities
Securities with no credit impairment in unrealized loss position		944
Investment securities available-for-sale, Amortized Cost	[1]	$ 14,767		13,397
Investment securities available-for-sale	[1]	$ 13,165		13,288
Commercial Mortgage Backed Securities
Securities with no credit impairment in unrealized loss position		239
Investment securities available-for-sale, Amortized Cost	[1]	$ 5,093		709
Investment securities available-for-sale	[1]	$ 4,862		$ 705
[1] Issued and/or guaranteed by U.S. government agencies or U.S. government-sponsored enterprises.

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