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			6 Months Ended			12 Months Ended
	Jun. 30, 2024		Jun. 30, 2023	Jun. 30, 2024		Jun. 30, 2023	Dec. 31, 2023		Dec. 31, 2022
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Balance, beginning of period	$ 2,318		$ 2,215	$ 2,322	[1]	$ 2,194	$ 2,194
Losses charged off	(182)		(121)	(328)		(231)
Recoveries of losses previously charged off	38		31	74		63
Provision for (benefit from) loan and lease losses	114		202	220		350
Balance, end of period	2,288	[1]	2,327	2,288	[1]	2,327	$ 2,322	[1]	$ 2,194
Accounting Standards Update [Extensible Enumeration]							Accounting Standards Update 2023-02 [Member]		Accounting Standards Update 2022-02 [Member]
Cumulative Effect, Period of Adoption, Adjustment
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Balance, beginning of period						(49)	$ (49)
Balance, end of period									$ (49)
Other Consumer Loans, Point of Sale
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Losses charged off	(7)		(8)	(15)		(17)
Recoveries of losses previously charged off	7		8	15		17
Commercial
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Balance, beginning of period	1,141		1,143	1,130		1,127	1,127
Losses charged off	(83)		(35)	(123)		(69)
Recoveries of losses previously charged off	3		3	8		6
Provision for (benefit from) loan and lease losses	52		88	98		131
Balance, end of period	1,113		1,199	1,113		1,199	1,130		1,127
Commercial | Cumulative Effect, Period of Adoption, Adjustment
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Balance, beginning of period						4	4
Balance, end of period									4
Residential Mortgage
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Balance, beginning of period	140		185	145		245	245
Losses charged off	(1)		(1)	(1)		(2)
Recoveries of losses previously charged off	1		1	2		2
Provision for (benefit from) loan and lease losses	(4)		(12)	(10)		(36)
Balance, end of period	136		173	136		173	145		245
Residential Mortgage | Cumulative Effect, Period of Adoption, Adjustment
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Balance, beginning of period						(36)	(36)
Balance, end of period									(36)
Consumer
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Balance, beginning of period	1,037		887	1,047		822	822
Losses charged off	(98)		(85)	(204)		(160)
Recoveries of losses previously charged off	34		27	64		55
Provision for (benefit from) loan and lease losses	66		126	132		255
Balance, end of period	$ 1,039		$ 955	$ 1,039		955	1,047		822
Consumer | Cumulative Effect, Period of Adoption, Adjustment
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Balance, beginning of period						$ (17)	$ (17)
Balance, end of period									$ (17)

[1] Includes $52 and $55 of other short-term investments, $1,272 and $1,573 of portfolio loans and leases, $(23) and $(28) of ALLL, $7 and $10 of other assets, $13 and $14 of other liabilities and $1,136 and $1,409 of long-term debt from consolidated VIEs that are included in their respective captions above at June 30, 2024 and December 31, 2023, respectively. For further information, refer to Note 11.