Credit Quality and the Allowance for Loan and Lease Losses - Summary of Transactions in the ALLL by Portfolio Segment (Details) - USD ($) $ in Millions	3 Months Ended			9 Months Ended
	Sep. 30, 2025		Sep. 30, 2024	Sep. 30, 2025		Sep. 30, 2024
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Balance, beginning of period	$ 2,412		$ 2,288	$ 2,352	[1]	$ 2,322
Losses charged off	(382)		(183)	(748)		(511)
Recoveries of losses previously charged off	43		41	134		115
Provision for (benefit from) loan and lease losses	192		159	527		379
Balance, end of period	2,265	[1]	2,305	2,265	[1]	2,305
Other Consumer Loans, Point of Sale
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Losses charged off	(4)		(6)	(15)		(22)
Recoveries of losses previously charged off	4		6	15		22
Commercial
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Balance, beginning of period	1,293		1,113	1,154		1,130
Losses charged off	(282)		(80)	(439)		(203)
Recoveries of losses previously charged off	7		8	28		16
Provision for (benefit from) loan and lease losses	164		64	439		162
Balance, end of period	1,182		1,105	1,182		1,105
Residential Mortgage
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Balance, beginning of period	134		136	146		145
Losses charged off	0		0	(1)		(2)
Recoveries of losses previously charged off	1		1	3		3
Provision for (benefit from) loan and lease losses	(2)		6	(15)		(3)
Balance, end of period	133		143	133		143
Consumer
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Balance, beginning of period	985		1,039	1,052		1,047
Losses charged off	(100)		(103)	(308)		(306)
Recoveries of losses previously charged off	35		32	103		96
Provision for (benefit from) loan and lease losses	30		89	103		220
Balance, end of period	$ 950		$ 1,057	$ 950		$ 1,057

[1] Includes $42 and $51 of other short-term investments, $649 and $1,000 of portfolio loans and leases, $(11) and $(19) of ALLL, $4 and $5 of other assets, $11 and $12 of other liabilities and $563 and $889 of long-term debt from consolidated VIEs that are included in their respective captions above at September 30, 2025 and December 31, 2024, respectively. For further information, refer to Note 7.