Investment Securities - Schedule of Investments Classified by Contractual Maturity Date (Details) - USD ($) $ in Millions	Sep. 30, 2024	Dec. 31, 2023
Amount
Total available-for-sale securities	$ 23,905	$ 24,415
Due in one year or less	561	449
Due after one year through five years	2,486	2,672
Due after five years through ten years	3,416	3,279
Due after ten years	$ 17,442	$ 18,015
Yield
Total	2.50%	2.50%
Due in one year or less	1.80%	1.70%
Due after one year through five years	2.20%	2.10%
Due after five years through ten years	2.50%	2.40%
Due after ten years	2.50%	2.50%
Amortized cost of available-for-sale securities
Total	$ 27,312	$ 28,416
Due in one year or less	565	461
Due after one year through five years	2,596	2,844
Due after five years through ten years	3,767	3,746
Due after ten years	20,384	21,365
Amount
Total	4,441	4,680
Due in one year or less	0	1
Due after one year through five years	67	41
Due after five years through ten years	41	14
Due after ten years	$ 4,333	$ 4,624
Yield
Total	2.90%	2.80%
Due in one year or less	0.00%	5.60%
Due after one year through five years	5.40%	5.60%
Due after five years through ten years	5.00%	3.40%
Due after ten years	2.80%	2.80%
Cash equivalents	$ 426	$ 36
U.S. Treasury and federal agencies
Amount
Total available-for-sale securities	2,115	2,075
Due in one year or less	253	215
Due after one year through five years	1,100	1,120
Due after five years through ten years	762	740
Due after ten years	$ 0	$ 0
Yield
Total	1.60%	1.60%
Due in one year or less	0.80%	0.90%
Due after one year through five years	1.50%	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	$ 2,270	$ 2,284
U.S. States and political subdivisions
Amount
Total available-for-sale securities	647	658
Due in one year or less	32	4
Due after one year through five years	69	55
Due after five years through ten years	94	110
Due after ten years	$ 452	$ 489
Yield
Total	3.40%	3.20%
Due in one year or less	6.70%	3.40%
Due after one year through five years	3.00%	2.70%
Due after five years through ten years	4.00%	3.60%
Due after ten years	3.20%	3.10%
Amortized cost of available-for-sale securities
Total	$ 718	$ 727
Foreign government
Amount
Total available-for-sale securities	200	183
Due in one year or less	39	20
Due after one year through five years	50	82
Due after five years through ten years	107	81
Due after ten years	$ 4	$ 0
Yield
Total	2.60%	2.30%
Due in one year or less	1.90%	1.30%
Due after one year through five years	2.30%	2.40%
Due after five years through ten years	2.90%	2.50%
Due after ten years	3.30%	0.00%
Amortized cost of available-for-sale securities
Total	$ 203	$ 190
Agency mortgage-backed residential
Amount
Total available-for-sale securities	14,697	15,384
Due in one year or less	0	0
Due after one year through five years	8	10
Due after five years through ten years	26	32
Due after ten years	$ 14,663	$ 15,342
Yield
Total	2.60%	2.60%
Due in one year or less	0.00%	0.00%
Due after one year through five years	2.00%	1.90%
Due after five years through ten years	2.50%	2.50%
Due after ten years	2.60%	2.60%
Amortized cost of available-for-sale securities
Total	$ 17,094	$ 18,122
Amount
Total	950	999
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	$ 950	$ 999
Yield
Total	2.70%	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	0.00%	0.00%
Due after ten years	2.70%	2.80%
Hedged asset, fair value hedge, cumulative increase (decrease)	$ 100	$ 46
Mortgage-backed residential
Amount
Total available-for-sale securities	219	225
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	$ 219	$ 225
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	$ 254	$ 268
Amount
Total	3,392	3,603
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	12
Due after ten years	$ 3,383	$ 3,591
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	3.00%	3.00%
Due after ten years	2.80%	2.80%
Agency mortgage-backed commercial
Amount
Total available-for-sale securities	$ 4,016	$ 3,758
Due in one year or less	23	0
Due after one year through five years	273	163
Due after five years through ten years	1,694	1,641
Due after ten years	$ 2,026	$ 1,954
Yield
Total	2.40%	2.30%
Due in one year or less	3.10%	0.00%
Due after one year through five years	3.70%	3.80%
Due after five years through ten years	2.40%	2.40%
Due after ten years	2.20%	2.10%
Amortized cost of available-for-sale securities
Total	$ 4,675	$ 4,539
Yield
Hedged asset, fair value hedge, cumulative increase (decrease)	57	29
Asset-backed
Amount
Total available-for-sale securities	202	332
Due in one year or less	0	0
Due after one year through five years	197	327
Due after five years through ten years	4	4
Due after ten years	$ 1	$ 1
Yield
Total	1.60%	1.70%
Due in one year or less	0.00%	0.00%
Due after one year through five years	1.60%	1.70%
Due after five years through ten years	3.90%	3.90%
Due after ten years	2.70%	2.70%
Amortized cost of available-for-sale securities
Total	$ 204	$ 344
Amount
Total	99	78
Due in one year or less	0	1
Due after one year through five years	67	41
Due after five years through ten years	32	2
Due after ten years	$ 0	$ 34
Yield
Total	5.40%	5.60%
Due in one year or less	0.00%	5.60%
Due after one year through five years	5.40%	5.60%
Due after five years through ten years	5.50%	6.00%
Due after ten years	0.00%	5.60%
Corporate debt
Amount
Total available-for-sale securities	$ 1,809	$ 1,800
Due in one year or less	214	210
Due after one year through five years	789	915
Due after five years through ten years	729	671
Due after ten years	$ 77	$ 4
Yield
Total	3.00%	2.70%
Due in one year or less	3.00%	2.40%
Due after one year through five years	2.60%	2.60%
Due after five years through ten years	3.20%	2.90%
Due after ten years	5.20%	6.20%
Amortized cost of available-for-sale securities
Total	$ 1,894	$ 1,942