Investment Securities (Investment Portfolio) (Details) - USD ($)	Sep. 30, 2023	Dec. 31, 2022
Available-for-sale securities
Total	$ 33,265,000,000	$ 34,863,000,000
Gross unrealized gains	0	5,000,000
Gross unrealized losses	(6,471,000,000)	(5,327,000,000)
Fair value	26,794,000,000	29,541,000,000
Held-to-maturity securities
Amortized cost	1,013,000,000	1,062,000,000
Gross unrealized gains	0	0
Gross unrealized losses	(234,000,000)	(178,000,000)
Fair value	779,000,000	884,000,000
Debt securities, available-for-sale, accrued interest receivable	$ 86,000,000	$ 91,000,000
Debt Securities, Available-for-Sale, Accrued Interest, after Allowance for Credit Loss, Statement of Financial Position [Extensible Enumeration]	Other assets	Other assets
Debt securities, available-for-sale, allowance for credit loss, excluding accrued interest	$ 0	$ 0
Debt securities, held-to-maturity, allowance for credit loss, excluding accrued interest	0	0
Debt securities, held-to-maturity, accrued interest receivable	2,000,000	2,000,000
Operating Segments | Insurance operations
Held-to-maturity securities
Deposit securities	12,000,000	12,000,000
Asset Pledged as Collateral with Right
Available-for-sale securities
Fair value	4,400,000,000	3,900,000,000
Held-to-maturity securities
Securities with the right to sell or pledge	1,300,000,000	899,000,000
Asset Pledged as Collateral with Right | Federal Home Loan Bank advances
Held-to-maturity securities
Securities with the right to sell or pledge	3,100,000,000	3,000,000,000
U.S. Treasury and federal agencies
Available-for-sale securities
Total	2,280,000,000	2,272,000,000
Gross unrealized gains	0	0
Gross unrealized losses	(289,000,000)	(256,000,000)
Fair value	1,991,000,000	2,016,000,000
U.S. States and political subdivisions
Available-for-sale securities
Total	729,000,000	841,000,000
Gross unrealized gains	0	1,000,000
Gross unrealized losses	(117,000,000)	(82,000,000)
Fair value	612,000,000	760,000,000
Foreign government
Available-for-sale securities
Total	175,000,000	158,000,000
Gross unrealized gains	0	0
Gross unrealized losses	(16,000,000)	(12,000,000)
Fair value	159,000,000	146,000,000
Agency mortgage-backed security
Available-for-sale securities
Total	18,434,000,000	19,668,000,000
Gross unrealized gains	0	3,000,000
Gross unrealized losses	(3,798,000,000)	(3,038,000,000)
Fair value	14,636,000,000	16,633,000,000
Held-to-maturity securities
Amortized cost	1,013,000,000	1,062,000,000
Gross unrealized gains	0	0
Gross unrealized losses	(234,000,000)	(178,000,000)
Fair value	779,000,000	884,000,000
Hedged liability, fair value hedge, cumulative increase (decrease)	148,000,000	12,000,000
Mortgage-backed residential
Available-for-sale securities
Total	4,858,000,000	5,154,000,000
Gross unrealized gains	0	0
Gross unrealized losses	(985,000,000)	(855,000,000)
Fair value	3,873,000,000	4,299,000,000
Agency mortgage-backed commercial
Available-for-sale securities
Total	4,497,000,000	4,380,000,000
Gross unrealized gains	0	0
Gross unrealized losses	(1,031,000,000)	(845,000,000)
Fair value	3,466,000,000	3,535,000,000
Held-to-maturity securities
Hedged liability, fair value hedge, cumulative increase (decrease)	86,000,000
Hedged asset, fair value hedge, cumulative increase (decrease)		15,000,000
Asset-backed
Available-for-sale securities
Total	370,000,000	459,000,000
Gross unrealized gains	0	0
Gross unrealized losses	(16,000,000)	(26,000,000)
Fair value	354,000,000	433,000,000
Corporate debt
Available-for-sale securities
Total	1,922,000,000	1,931,000,000
Gross unrealized gains	0	1,000,000
Gross unrealized losses	(219,000,000)	(213,000,000)
Fair value	$ 1,703,000,000	$ 1,719,000,000