Investment Securities - Schedule of Investments Classified by Contractual Maturity Date (Details) - USD ($) $ in Millions	Sep. 30, 2025	Dec. 31, 2024
Amount
Total available-for-sale securities	$ 22,684	$ 22,410
Due in one year or less	342	327
Due after one year through five years	3,938	2,438
Due after five years through ten years	3,285	3,371
Due after ten years	$ 15,119	$ 16,274
Yield
Total	3.00%	2.50%
Due in one year or less	1.90%	2.30%
Due after one year through five years	3.40%	2.20%
Due after five years through ten years	2.90%	2.60%
Due after ten years	2.90%	2.60%
Amortized cost of available-for-sale securities
Amortized cost	$ 25,660	$ 26,810
Due in one year or less	345	330
Due after one year through five years	3,999	2,579
Due after five years through ten years	3,596	3,844
Due after ten years	17,720	20,057
Amount
Amortized cost	4,433	4,346
Due in one year or less	0	0
Due after one year through five years	41	64
Due after five years through ten years	24	33
Due after ten years	$ 4,368	$ 4,249
Yield
Total	3.00%	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	$ 373	$ 106
U.S. Treasury and federal agencies
Amount
Total available-for-sale securities	2,194	1,873
Due in one year or less	84	54
Due after one year through five years	1,640	1,087
Due after five years through ten years	470	732
Due after ten years	$ 0	$ 0
Yield
Total	3.40%	1.60%
Due in one year or less	0.90%	1.00%
Due after one year through five years	4.00%	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
Amortized cost	$ 2,230	$ 2,073
U.S. States and political subdivisions
Amount
Total available-for-sale securities	554	617
Due in one year or less	45	33
Due after one year through five years	60	72
Due after five years through ten years	61	86
Due after ten years	$ 388	$ 426
Yield
Total	3.40%	3.40%
Due in one year or less	4.90%	6.20%
Due after one year through five years	3.80%	3.10%
Due after five years through ten years	4.20%	4.10%
Due after ten years	3.10%	3.20%
Amortized cost of available-for-sale securities
Amortized cost	$ 634	$ 704
Foreign government
Amount
Total available-for-sale securities	204	194
Due in one year or less	20	33
Due after one year through five years	80	51
Due after five years through ten years	104	110
Due after ten years	$ 0	$ 0
Yield
Total	2.80%	2.70%
Due in one year or less	2.00%	2.10%
Due after one year through five years	2.30%	2.50%
Due after five years through ten years	3.30%	2.90%
Due after ten years	0.00%	0.00%
Amortized cost of available-for-sale securities
Amortized cost	$ 205	$ 198
Agency mortgage-backed residential
Amount
Total available-for-sale securities	12,822	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	0	23
Due after ten years	$ 12,821	$ 13,623
Yield
Total	3.00%	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	0.00%	2.50%
Due after ten years	3.00%	2.60%
Amortized cost of available-for-sale securities
Amortized cost	$ 14,965	$ 16,765
Amount
Amortized cost	1,284	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	$ 1,284	$ 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 asset, fair value hedge, cumulative increase (decrease)	$ 53
Hedged liability, fair value hedge, cumulative increase (decrease)		$ 72
Mortgage-backed residential
Amount
Total available-for-sale securities	200	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	$ 200	$ 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
Amortized cost	$ 235	$ 249
Amount
Amortized cost	3,091	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	7	9
Due after ten years	$ 3,084	$ 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	$ 4,782	$ 3,984
Due in one year or less	0	23
Due after one year through five years	1,225	339
Due after five years through ten years	2,004	1,724
Due after ten years	$ 1,553	$ 1,898
Yield
Total	2.70%	2.50%
Due in one year or less	0.00%	3.10%
Due after one year through five years	3.50%	3.70%
Due after five years through ten years	2.60%	2.50%
Due after ten years	2.20%	2.10%
Amortized cost of available-for-sale securities
Amortized cost	$ 5,415	$ 4,819
Yield
Hedged asset, fair value hedge, cumulative increase (decrease)	40
Hedged liability, fair value hedge, cumulative increase (decrease)		34
Asset-backed
Amount
Total available-for-sale securities	25	129
Due in one year or less	0	0
Due after one year through five years	25	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	0.00%	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
Amortized cost	$ 25	$ 131
Amount
Amortized cost	58	88
Due in one year or less	0	0
Due after one year through five years	41	64
Due after five years through ten years	17	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	5.70%	5.60%
Due after ten years	0.00%	0.00%
Corporate debt
Amount
Total available-for-sale securities	$ 1,903	$ 1,754
Due in one year or less	193	184
Due after one year through five years	907	754
Due after five years through ten years	646	695
Due after ten years	$ 157	$ 121
Yield
Total	3.40%	3.10%
Due in one year or less	2.60%	3.00%
Due after one year through five years	2.50%	2.60%
Due after five years through ten years	4.50%	3.30%
Due after ten years	5.50%	5.30%
Amortized cost of available-for-sale securities
Amortized cost	$ 1,951	$ 1,871