Investment Securities (Investments Classified by Contractual Maturity Date) (Details) - USD ($) $ in Millions	Mar. 31, 2024	Dec. 31, 2023
Amount
Total available-for-sale securities	$ 23,684	$ 24,415
Due in one year or less	455	449
Due after one year through five years	2,625	2,672
Due after five years through ten years	3,255	3,279
Due after ten years	$ 17,349	$ 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	2.10%	2.10%
Due after five years through ten years	2.40%	2.40%
Due after ten years	2.50%	2.50%
Amortized cost of available-for-sale securities
Total	$ 28,114	$ 28,416
Due in one year or less	465	461
Due after one year through five years	2,808	2,844
Due after five years through ten years	3,762	3,746
Due after ten years	21,079	21,365
Amount
Total	4,655	4,680
Due in one year or less	13	1
Due after one year through five years	76	41
Due after five years through ten years	48	14
Due after ten years	$ 4,518	$ 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	4.90%	3.40%
Due after ten years	3.80%	2.80%
Cash equivalents	$ 386	$ 36
U.S. Treasury and federal agencies
Amount
Total available-for-sale securities	2,057	2,075
Due in one year or less	218	215
Due after one year through five years	1,112	1,120
Due after five years through ten years	727	740
Due after ten years	$ 0	$ 0
Yield
Total	1.60%	1.60%
Due in one year or less	0.90%	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	$ 2,286	$ 2,284
U.S. States and political subdivisions
Amount
Total available-for-sale securities	643	658
Due in one year or less	4	4
Due after one year through five years	61	55
Due after five years through ten years	102	110
Due after ten years	$ 476	$ 489
Yield
Total	3.20%	3.20%
Due in one year or less	3.20%	3.40%
Due after one year through five years	3.00%	2.70%
Due after five years through ten years	3.60%	3.60%
Due after ten years	3.20%	3.10%
Amortized cost of available-for-sale securities
Total	$ 720	$ 727
Foreign government
Amount
Total available-for-sale securities	182	183
Due in one year or less	23	20
Due after one year through five years	77	82
Due after five years through ten years	82	81
Due after ten years	$ 0	$ 0
Yield
Total	2.40%	2.30%
Due in one year or less	1.80%	1.30%
Due after one year through five years	2.50%	2.40%
Due after five years through ten years	2.50%	2.50%
Due after ten years	0.00%	0.00%
Amortized cost of available-for-sale securities
Total	$ 191	$ 190
Agency mortgage-backed residential
Amount
Total available-for-sale securities	14,752	15,384
Due in one year or less	0	0
Due after one year through five years	9	10
Due after five years through ten years	30	32
Due after ten years	$ 14,713	$ 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	$ 17,831	$ 18,122
Amount
Total	984	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	$ 984	$ 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)	$ 77
Hedged asset, fair value hedge, cumulative increase (decrease)		$ 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	$ 264	$ 268
Amount
Total	3,544	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	$ 3,533	$ 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	$ 3,800	$ 3,758
Due in one year or less	0	0
Due after one year through five years	184	163
Due after five years through ten years	1,680	1,641
Due after ten years	$ 1,936	$ 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	3.90%	3.80%
Due after five years through ten years	2.40%	2.40%
Due after ten years	2.10%	2.10%
Amortized cost of available-for-sale securities
Total	$ 4,634	$ 4,539
Yield
Hedged liability, fair value hedge, cumulative increase (decrease)	32
Hedged asset, fair value hedge, cumulative increase (decrease)		29
Asset-backed
Amount
Total available-for-sale securities	301	332
Due in one year or less	0	0
Due after one year through five years	297	327
Due after five years through ten years	4	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	$ 310	$ 344
Amount
Total	127	78
Due in one year or less	13	1
Due after one year through five years	76	41
Due after five years through ten years	37	2
Due after ten years	$ 1	$ 34
Yield
Total	5.50%	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	6.80%	5.60%
Corporate debt
Amount
Total available-for-sale securities	$ 1,730	$ 1,800
Due in one year or less	210	210
Due after one year through five years	885	915
Due after five years through ten years	630	671
Due after ten years	$ 5	$ 4
Yield
Total	2.70%	2.70%
Due in one year or less	2.60%	2.40%
Due after one year through five years	2.60%	2.60%
Due after five years through ten years	2.90%	2.90%
Due after ten years	6.10%	6.20%
Amortized cost of available-for-sale securities
Total	$ 1,878	$ 1,942