Investment Securities - Schedule of Investment Portfolio (Details) - USD ($)	6 Months Ended
	Jun. 30, 2025	Mar. 31, 2025	Dec. 31, 2024
Available-for-sale securities
Amortized cost	$ 25,715,000,000		$ 26,810,000,000
Gross unrealized gains	44,000,000		5,000,000
Gross unrealized losses	(3,362,000,000)		(4,405,000,000)
Fair value	22,397,000,000		22,410,000,000
Held-to-maturity securities
Amortized cost	4,561,000,000		4,346,000,000
Gross unrealized gains	173,000,000		143,000,000
Gross unrealized losses	(175,000,000)		(196,000,000)
Fair value	4,559,000,000		4,293,000,000
Debt securities, available-for-sale, accrued interest receivable	$ 85,000,000		$ 73,000,000
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	13,000,000		12,000,000
Amortized cost basis in amount sold		$ 4,600,000,000
Gross proceeds received and receivable from sale of lower-yielding available-for-sale securities	4,100,000,000
Pre-tax loss	495,000,000
Operating Segments | Insurance operations
Held-to-maturity securities
Deposited securities	13,000,000		13,000,000
Asset Pledged as Collateral with Right
Available-for-sale securities
Fair value	4,200,000,000		3,400,000,000
Held-to-maturity securities
Securities with the right to sell or pledge	1,400,000,000		439,000,000
Asset Pledged as Collateral with Right | Federal Home Loan Bank advances
Held-to-maturity securities
Securities with the right to sell or pledge	2,800,000,000		2,900,000,000
U.S. Treasury and federal agencies
Available-for-sale securities
Amortized cost	2,216,000,000		2,073,000,000
Gross unrealized gains	16,000,000		0
Gross unrealized losses	(61,000,000)		(200,000,000)
Fair value	2,171,000,000		1,873,000,000
U.S. States and political subdivisions
Available-for-sale securities
Amortized cost	669,000,000		704,000,000
Gross unrealized gains	0		0
Gross unrealized losses	(93,000,000)		(87,000,000)
Fair value	576,000,000		617,000,000
Foreign government
Available-for-sale securities
Amortized cost	197,000,000		198,000,000
Gross unrealized gains	1,000,000		1,000,000
Gross unrealized losses	(4,000,000)		(5,000,000)
Fair value	194,000,000		194,000,000
Agency mortgage-backed residential
Available-for-sale securities
Amortized cost	15,032,000,000		16,765,000,000
Gross unrealized gains	4,000,000		0
Gross unrealized losses	(2,381,000,000)		(3,112,000,000)
Fair value	12,655,000,000		13,653,000,000
Held-to-maturity securities
Amortized cost	1,310,000,000		935,000,000
Gross unrealized gains	1,000,000		0
Gross unrealized losses	(175,000,000)		(196,000,000)
Fair value	1,136,000,000		739,000,000
Hedged asset, fair value hedge, cumulative increase (decrease)	47,000,000
Hedged liability, fair value hedge, cumulative increase (decrease)			72,000,000
Mortgage-backed residential
Available-for-sale securities
Amortized cost	240,000,000		249,000,000
Gross unrealized gains	0		0
Gross unrealized losses	(39,000,000)		(43,000,000)
Fair value	201,000,000		206,000,000
Held-to-maturity securities
Amortized cost	3,184,000,000		3,323,000,000
Gross unrealized gains	171,000,000		142,000,000
Gross unrealized losses	0		0
Fair value	3,355,000,000		3,465,000,000
Agency mortgage-backed commercial
Available-for-sale securities
Amortized cost	5,388,000,000		4,819,000,000
Gross unrealized gains	11,000,000		1,000,000
Gross unrealized losses	(702,000,000)		(836,000,000)
Fair value	4,697,000,000		3,984,000,000
Held-to-maturity securities
Hedged asset, fair value hedge, cumulative increase (decrease)	36,000,000
Hedged liability, fair value hedge, cumulative increase (decrease)			34,000,000
Asset-backed
Available-for-sale securities
Amortized cost	45,000,000		131,000,000
Gross unrealized gains	0		0
Gross unrealized losses	0		(2,000,000)
Fair value	45,000,000		129,000,000
Held-to-maturity securities
Amortized cost	67,000,000		88,000,000
Gross unrealized gains	1,000,000		1,000,000
Gross unrealized losses	0		0
Fair value	68,000,000		89,000,000
Corporate debt
Available-for-sale securities
Amortized cost	1,928,000,000		1,871,000,000
Gross unrealized gains	12,000,000		3,000,000
Gross unrealized losses	(82,000,000)		(120,000,000)
Fair value	$ 1,858,000,000		$ 1,754,000,000