Investment Securities - Schedule of Investments Classified by Contractual Maturity Date (Details) - USD ($) $ in Millions	Mar. 31, 2025	Dec. 31, 2024
Amount
Total available-for-sale securities	$ 22,346	$ 22,410
Due in one year or less	327	327
Due after one year through five years	3,460	2,438
Due after five years through ten years	3,481	3,371
Due after ten years	$ 15,078	$ 16,274
Yield
Total	2.90%	2.50%
Due in one year or less	2.30%	2.30%
Due after one year through five years	3.60%	2.20%
Due after five years through ten years	3.00%	2.60%
Due after ten years	2.80%	2.60%
Amortized cost of available-for-sale securities
Total	$ 25,772	$ 26,810
Due in one year or less	330	330
Due after one year through five years	3,510	2,579
Due after five years through ten years	3,838	3,844
Due after ten years	18,094	20,057
Amount
Total	4,668	4,346
Due in one year or less	0	0
Due after one year through five years	55	64
Due after five years through ten years	31	33
Due after ten years	$ 4,582	$ 4,249
Yield
Total	3.10%	2.90%
Due in one year or less	0.00%	0.00%
Due after one year through five years	5.30%	5.30%
Due after five years through ten years	5.00%	5.00%
Due after ten years	3.00%	2.80%
Cash equivalents	$ 451	$ 106
U.S. Treasury and federal agencies
Amount
Total available-for-sale securities	2,086	1,873
Due in one year or less	39	54
Due after one year through five years	1,590	1,087
Due after five years through ten years	457	732
Due after ten years	$ 0	$ 0
Yield
Total	3.40%	1.60%
Due in one year or less	0.70%	1.00%
Due after one year through five years	3.90%	1.50%
Due after five years through ten years	1.90%	1.90%
Due after ten years	0.00%	0.00%
Amortized cost of available-for-sale securities
Total	$ 2,150	$ 2,073
U.S. States and political subdivisions
Amount
Total available-for-sale securities	610	617
Due in one year or less	39	33
Due after one year through five years	68	72
Due after five years through ten years	85	86
Due after ten years	$ 418	$ 426
Yield
Total	3.50%	3.40%
Due in one year or less	5.60%	6.20%
Due after one year through five years	3.40%	3.10%
Due after five years through ten years	4.10%	4.10%
Due after ten years	3.20%	3.20%
Amortized cost of available-for-sale securities
Total	$ 700	$ 704
Foreign government
Amount
Total available-for-sale securities	199	194
Due in one year or less	27	33
Due after one year through five years	63	51
Due after five years through ten years	109	110
Due after ten years	$ 0	$ 0
Yield
Total	2.70%	2.70%
Due in one year or less	2.10%	2.10%
Due after one year through five years	2.50%	2.50%
Due after five years through ten years	2.90%	2.90%
Due after ten years	0.00%	0.00%
Amortized cost of available-for-sale securities
Total	$ 200	$ 198
Agency mortgage-backed residential
Amount
Total available-for-sale securities	12,687	13,653
Due in one year or less	0	0
Due after one year through five years	1	7
Due after five years through ten years	276	23
Due after ten years	$ 12,410	$ 13,623
Yield
Total	2.90%	2.60%
Due in one year or less	0.00%	0.00%
Due after one year through five years	2.80%	2.00%
Due after five years through ten years	5.50%	2.50%
Due after ten years	2.80%	2.60%
Amortized cost of available-for-sale securities
Total	$ 15,096	$ 16,765
Amount
Total	1,332	935
Due in one year or less	0	0
Due after one year through five years	0	0
Due after five years through ten years	0	0
Due after ten years	$ 1,332	$ 935
Yield
Total	3.50%	2.70%
Due in one year or less	0.00%	0.00%
Due after one year through five years	0.00%	0.00%
Due after five years through ten years	0.00%	0.00%
Due after ten years	3.50%	2.70%
Hedged liability, fair value hedge, cumulative increase (decrease)		$ 72
Mortgage-backed residential
Amount
Total available-for-sale securities	$ 205	206
Due in one year or less	0	0
Due after one year through five years	0	0
Due after five years through ten years	0	0
Due after ten years	$ 205	$ 206
Yield
Total	2.70%	2.70%
Due in one year or less	0.00%	0.00%
Due after one year through five years	0.00%	0.00%
Due after five years through ten years	0.00%	0.00%
Due after ten years	2.70%	2.70%
Amortized cost of available-for-sale securities
Total	$ 245	$ 249
Amount
Total	3,259	3,323
Due in one year or less	0	0
Due after one year through five years	0	0
Due after five years through ten years	9	9
Due after ten years	$ 3,250	$ 3,314
Yield
Total	2.80%	2.80%
Due in one year or less	0.00%	0.00%
Due after one year through five years	0.00%	0.00%
Due after five years through ten years	3.40%	3.10%
Due after ten years	2.80%	2.80%
Agency mortgage-backed commercial
Amount
Total available-for-sale securities	$ 4,671	$ 3,984
Due in one year or less	23	23
Due after one year through five years	930	339
Due after five years through ten years	1,815	1,724
Due after ten years	$ 1,903	$ 1,898
Yield
Total	2.70%	2.50%
Due in one year or less	3.10%	3.10%
Due after one year through five years	4.00%	3.70%
Due after five years through ten years	2.60%	2.50%
Due after ten years	2.10%	2.10%
Amortized cost of available-for-sale securities
Total	$ 5,399	$ 4,819
Yield
Hedged liability, fair value hedge, cumulative increase (decrease)		34
Asset-backed
Amount
Total available-for-sale securities	74	129
Due in one year or less	1	0
Due after one year through five years	73	128
Due after five years through ten years	0	1
Due after ten years	$ 0	$ 0
Yield
Total	1.50%	1.50%
Due in one year or less	3.30%	0.00%
Due after one year through five years	1.50%	1.50%
Due after five years through ten years	0.00%	4.00%
Due after ten years	0.00%	0.00%
Amortized cost of available-for-sale securities
Total	$ 75	$ 131
Amount
Total	77	88
Due in one year or less	0	0
Due after one year through five years	55	64
Due after five years through ten years	22	24
Due after ten years	$ 0	$ 0
Yield
Total	5.40%	5.40%
Due in one year or less	0.00%	0.00%
Due after one year through five years	5.30%	5.30%
Due after five years through ten years	5.60%	5.60%
Due after ten years	0.00%	0.00%
Corporate debt
Amount
Total available-for-sale securities	$ 1,814	$ 1,754
Due in one year or less	198	184
Due after one year through five years	735	754
Due after five years through ten years	739	695
Due after ten years	$ 142	$ 121
Yield
Total	3.20%	3.10%
Due in one year or less	2.90%	3.00%
Due after one year through five years	2.60%	2.60%
Due after five years through ten years	3.60%	3.30%
Due after ten years	5.50%	5.30%
Amortized cost of available-for-sale securities
Total	$ 1,907	$ 1,871