AOCI (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2025	Jun. 30, 2024	Jun. 30, 2025	Jun. 30, 2024
AOCI, Net of Tax [Roll Forward]
Total OCI, net of tax	$ 357	$ 4,718	$ 1,320	$ 4,002
Pension and OPEB Costs
AOCI, Net of Tax [Roll Forward]
AOCI, beginning balance	(643)	(1,078)	(648)	(1,079)
OCI before reclassifications, net of tax(1)	1	34	6	35	[1]
Total OCI, net of tax	2	34	7	35
AOCI, ending balance	(641)	(1,044)	(641)	(1,044)
Pension and OPEB Costs | Amounts reclassified from AOCI
Amounts reclassified from AOCI:
Before tax	1	0	1	0
Tax effect	0	0	0	0
Amounts reclassified, net of tax	1	0	1	0
Cash Flow Hedges
AOCI, Net of Tax [Roll Forward]
AOCI, beginning balance	(432)	(490)	(861)	(300)
OCI before reclassifications, net of tax(1)	205	(99)	563	(331)	[1]
Total OCI, net of tax	275	(38)	704	(228)
AOCI, ending balance	(157)	(528)	(157)	(528)
Cash Flow Hedges | Amounts reclassified from AOCI
Amounts reclassified from AOCI:
Before tax	92	79	185	134
Tax effect	22	18	44	31
Amounts reclassified, net of tax	70	61	141	103
AFS Securities
AOCI, Net of Tax [Roll Forward]
AOCI, beginning balance	(4,095)	(9,354)	(4,573)	(8,778)
OCI before reclassifications, net of tax(1)	69	(325)	612	(780)	[1]
Total OCI, net of tax	16	4,664	494	4,088
AOCI, ending balance	(4,079)	(4,690)	(4,079)	(4,690)
AFS Securities | Amounts reclassified from AOCI
Amounts reclassified from AOCI:
Before tax	(66)	6,529	(151)	6,371
Tax effect	(13)	1,540	(33)	1,503
Amounts reclassified, net of tax	(53)	4,989	(118)	4,868
HTM Securities
AOCI, Net of Tax [Roll Forward]
AOCI, beginning balance	(2,075)	(2,296)	(2,125)	(2,347)
OCI before reclassifications, net of tax(1)	0	0	0	0	[1]
Total OCI, net of tax	59	57	109	108
AOCI, ending balance	(2,016)	(2,239)	(2,016)	(2,239)
HTM Securities | Amounts reclassified from AOCI
Amounts reclassified from AOCI:
Before tax	71	75	136	141
Tax effect	12	18	27	33
Amounts reclassified, net of tax	59	57	109	108
Other, net
AOCI, Net of Tax [Roll Forward]
AOCI, beginning balance	(5)	(4)	(6)	(2)
OCI before reclassifications, net of tax(1)	5	1	6	(1)	[1]
Total OCI, net of tax	5	1	6	(1)
AOCI, ending balance	0	(3)	0	(3)
Other, net | Amounts reclassified from AOCI
Amounts reclassified from AOCI:
Before tax	0	0	0	0
Tax effect	0	0	0	0
Amounts reclassified, net of tax	0	0	0	0
Total
AOCI, Net of Tax [Roll Forward]
AOCI, beginning balance	(7,250)	(13,222)	(8,213)	(12,506)
OCI before reclassifications, net of tax(1)	280	(389)	1,187	(1,077)	[1]
Total OCI, net of tax	357	4,718	1,320	4,002
AOCI, ending balance	(6,893)	(8,504)	(6,893)	(8,504)
Total | Amounts reclassified from AOCI
Amounts reclassified from AOCI:
Before tax	98	6,683	171	6,646
Tax effect	21	1,576	38	1,567
Amounts reclassified, net of tax	$ 77	$ 5,107	$ 133	$ 5,079

[1] Includes the impact of the remeasurement of the pension plan and the reduction of pension benefit obligations following the sale of TIH. Refer to “Note 13. Benefit Plans” for additional information.