Investment Securities - Schedule of Investments Classified by Contractual Maturity Date (Details) - USD ($) $ in Millions	Jun. 30, 2024	Dec. 31, 2023
Amount
Total available-for-sale securities	$ 23,200	$ 24,415
Due in one year or less	546	449
Due after one year through five years	2,525	2,672
Due after five years through ten years	3,207	3,279
Due after ten years	$ 16,922	$ 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	$ 27,705	$ 28,416
Due in one year or less	556	461
Due after one year through five years	2,705	2,844
Due after five years through ten years	3,704	3,746
Due after ten years	20,740	21,365
Amount
Total	4,548	4,680
Due in one year or less	4	1
Due after one year through five years	72	41
Due after five years through ten years	45	14
Due after ten years	$ 4,427	$ 4,624
Yield
Total	2.90%	2.80%
Due in one year or less	5.50%	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	$ 385	$ 36
U.S. Treasury and federal agencies
Amount
Total available-for-sale securities	2,047	2,075
Due in one year or less	256	215
Due after one year through five years	1,065	1,120
Due after five years through ten years	726	740
Due after ten years	$ 0	$ 0
Yield
Total	1.50%	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	$ 2,274	$ 2,284
U.S. States and political subdivisions
Amount
Total available-for-sale securities	622	658
Due in one year or less	5	4
Due after one year through five years	60	55
Due after five years through ten years	104	110
Due after ten years	$ 453	$ 489
Yield
Total	3.20%	3.20%
Due in one year or less	3.90%	3.40%
Due after one year through five years	3.00%	2.70%
Due after five years through ten years	3.80%	3.60%
Due after ten years	3.10%	3.10%
Amortized cost of available-for-sale securities
Total	$ 704	$ 727
Foreign government
Amount
Total available-for-sale securities	175	183
Due in one year or less	35	20
Due after one year through five years	53	82
Due after five years through ten years	87	81
Due after ten years	$ 0	$ 0
Yield
Total	2.50%	2.30%
Due in one year or less	1.90%	1.30%
Due after one year through five years	2.50%	2.40%
Due after five years through ten years	2.70%	2.50%
Due after ten years	0.00%	0.00%
Amortized cost of available-for-sale securities
Total	$ 183	$ 190
Agency mortgage-backed residential
Amount
Total available-for-sale securities	14,336	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	28	32
Due after ten years	$ 14,300	$ 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	1.90%	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	$ 17,491	$ 18,122
Amount
Total	966	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	$ 966	$ 999
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	0.00%	0.00%
Due after ten years	2.80%	2.80%
Hedged liability, fair value hedge, cumulative increase (decrease)	$ 94
Hedged asset, fair value hedge, cumulative increase (decrease)		$ 46
Mortgage-backed residential
Amount
Total available-for-sale securities	214	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	$ 214	$ 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	$ 259	$ 268
Amount
Total	3,472	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	11	12
Due after ten years	$ 3,461	$ 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	$ 3,812	$ 3,758
Due in one year or less	0	0
Due after one year through five years	266	163
Due after five years through ten years	1,609	1,641
Due after ten years	$ 1,937	$ 1,954
Yield
Total	2.40%	2.30%
Due in one year or less	0.00%	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	$ 4,650	$ 4,539
Yield
Hedged liability, fair value hedge, cumulative increase (decrease)	42
Hedged asset, fair value hedge, cumulative increase (decrease)		29
Asset-backed
Amount
Total available-for-sale securities	260	332
Due in one year or less	0	0
Due after one year through five years	255	327
Due after five years through ten years	5	4
Due after ten years	$ 0	$ 1
Yield
Total	1.70%	1.70%
Due in one year or less	0.00%	0.00%
Due after one year through five years	1.70%	1.70%
Due after five years through ten years	3.90%	3.90%
Due after ten years	0.00%	2.70%
Amortized cost of available-for-sale securities
Total	$ 266	$ 344
Amount
Total	110	78
Due in one year or less	4	1
Due after one year through five years	72	41
Due after five years through ten years	34	2
Due after ten years	$ 0	$ 34
Yield
Total	5.40%	5.60%
Due in one year or less	5.50%	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	$ 1,734	$ 1,800
Due in one year or less	250	210
Due after one year through five years	818	915
Due after five years through ten years	648	671
Due after ten years	$ 18	$ 4
Yield
Total	2.90%	2.70%
Due in one year or less	2.90%	2.40%
Due after one year through five years	2.60%	2.60%
Due after five years through ten years	3.10%	2.90%
Due after ten years	5.60%	6.20%
Amortized cost of available-for-sale securities
Total	$ 1,878	$ 1,942