Loans and Related Allowance for Credit Losses, Credit Quality Indicators for Other Consumer Loans by Vintage (Details) - Total Consumer [Member] - USD ($) $ in Millions	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023	Dec. 31, 2023
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, by Origination Year [Abstract]
Total loans	$ 379,069		$ 379,069		$ 389,255
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss, Writeoff, by Origination Year [Abstract]
Loan charge-offs, loans	1,016	$ 887	3,095	$ 2,466
Other consumer [Member]
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, by Origination Year [Abstract]
Term loans by origination year, current fiscal year, finance receivable	1,526		1,526		3,306
Term loans by origination year, fiscal year before current fiscal year, finance receivable	2,163		2,163		2,178
Term loans by origination year, two years before current fiscal year, finance receivable	1,385		1,385		583
Term loans by origination year, three years before current fiscal year, finance receivable	343		343		169
Term loans by origination year, four years before current fiscal year, finance receivable	94		94		94
Term loans by origination year, more than five years before current fiscal year, finance receivable	73		73		64
Revolving loans, finance receivable	22,818		22,818		22,020
Revolving loans converted to term loans, finance receivable	130		130		125
Total loans	28,532		28,532		28,539
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss, Writeoff, by Origination Year [Abstract]
Term loans by origination year, current fiscal year, charge-offs			100		178
Term loans by origination year, fiscal year before current fiscal year, charge-offs			133		158
Term loans by origination year, two years before current fiscal year, charge-offs			104		52
Term loans by origination year, three years before current fiscal year, charge-offs			27		9
Term loans by origination year, four years before current fiscal year, charge-offs			4		9
Term loans by origination year, more than five years before current fiscal year, charge-offs			4		6
Revolving loans, charge-offs			51		62
Revolving loans converted to term loans, charge-offs			8		11
Loan charge-offs, loans	144	$ 124	431	$ 339	485
Other consumer [Member] | FICO 740 or more [Member]
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, by Origination Year [Abstract]
Term loans by origination year, current fiscal year, finance receivable	1,141		1,141		1,911
Term loans by origination year, fiscal year before current fiscal year, finance receivable	1,066		1,066		926
Term loans by origination year, two years before current fiscal year, finance receivable	554		554		265
Term loans by origination year, three years before current fiscal year, finance receivable	144		144		85
Term loans by origination year, four years before current fiscal year, finance receivable	59		59		36
Term loans by origination year, more than five years before current fiscal year, finance receivable	32		32		28
Revolving loans, finance receivable	978		978		1,152
Revolving loans converted to term loans, finance receivable	41		41		27
Total loans	4,015		4,015		4,430
Other consumer [Member] | FICO 700 to 739 [Member]
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, by Origination Year [Abstract]
Term loans by origination year, current fiscal year, finance receivable	211		211		642
Term loans by origination year, fiscal year before current fiscal year, finance receivable	431		431		409
Term loans by origination year, two years before current fiscal year, finance receivable	249		249		107
Term loans by origination year, three years before current fiscal year, finance receivable	61		61		27
Term loans by origination year, four years before current fiscal year, finance receivable	14		14		14
Term loans by origination year, more than five years before current fiscal year, finance receivable	12		12		10
Revolving loans, finance receivable	424		424		507
Revolving loans converted to term loans, finance receivable	18		18		16
Total loans	1,420		1,420		1,732
Other consumer [Member] | FICO 660 to 699 [Member]
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, by Origination Year [Abstract]
Term loans by origination year, current fiscal year, finance receivable	77		77		403
Term loans by origination year, fiscal year before current fiscal year, finance receivable	330		330		365
Term loans by origination year, two years before current fiscal year, finance receivable	230		230		93
Term loans by origination year, three years before current fiscal year, finance receivable	52		52		16
Term loans by origination year, four years before current fiscal year, finance receivable	8		8		11
Term loans by origination year, more than five years before current fiscal year, finance receivable	9		9		8
Revolving loans, finance receivable	346		346		395
Revolving loans converted to term loans, finance receivable	17		17		16
Total loans	1,069		1,069		1,307
Other consumer [Member] | FICO 620 to 659 [Member]
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, by Origination Year [Abstract]
Term loans by origination year, current fiscal year, finance receivable	14		14		129
Term loans by origination year, fiscal year before current fiscal year, finance receivable	119		119		166
Term loans by origination year, two years before current fiscal year, finance receivable	105		105		45
Term loans by origination year, three years before current fiscal year, finance receivable	25		25		6
Term loans by origination year, four years before current fiscal year, finance receivable	3		3		6
Term loans by origination year, more than five years before current fiscal year, finance receivable	6		6		5
Revolving loans, finance receivable	126		126		147
Revolving loans converted to term loans, finance receivable	11		11		11
Total loans	409		409		515
Other consumer [Member] | FICO less than 620 [Member]
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, by Origination Year [Abstract]
Term loans by origination year, current fiscal year, finance receivable	7		7		75
Term loans by origination year, fiscal year before current fiscal year, finance receivable	112		112		152
Term loans by origination year, two years before current fiscal year, finance receivable	119		119		49
Term loans by origination year, three years before current fiscal year, finance receivable	39		39		8
Term loans by origination year, four years before current fiscal year, finance receivable	4		4		8
Term loans by origination year, more than five years before current fiscal year, finance receivable	7		7		6
Revolving loans, finance receivable	142		142		152
Revolving loans converted to term loans, finance receivable	18		18		17
Total loans	448		448		467
Other consumer [Member] | No FICO available [Member]
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, by Origination Year [Abstract]
Term loans by origination year, current fiscal year, finance receivable	76		76		146
Term loans by origination year, fiscal year before current fiscal year, finance receivable	105		105		160
Term loans by origination year, two years before current fiscal year, finance receivable	128		128		24
Term loans by origination year, three years before current fiscal year, finance receivable	22		22		27
Term loans by origination year, four years before current fiscal year, finance receivable	6		6		19
Term loans by origination year, more than five years before current fiscal year, finance receivable	7		7		7
Revolving loans, finance receivable	20,802		20,802		19,667
Revolving loans converted to term loans, finance receivable	25		25		38
Total loans	21,171		21,171		20,088
Other consumer [Member] | Current-29 days past due and still accruing [Member]
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, by Origination Year [Abstract]
Term loans by origination year, current fiscal year, finance receivable	1,522		1,522		3,273
Term loans by origination year, fiscal year before current fiscal year, finance receivable	2,129		2,129		2,132
Term loans by origination year, two years before current fiscal year, finance receivable	1,354		1,354		571
Term loans by origination year, three years before current fiscal year, finance receivable	337		337		167
Term loans by origination year, four years before current fiscal year, finance receivable	93		93		93
Term loans by origination year, more than five years before current fiscal year, finance receivable	70		70		61
Revolving loans, finance receivable	22,782		22,782		21,988
Revolving loans converted to term loans, finance receivable	114		114		106
Total loans	28,401		28,401		28,391
Other consumer [Member] | 30 to 89 days past due [Member]
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, by Origination Year [Abstract]
Term loans by origination year, current fiscal year, finance receivable	3		3		24
Term loans by origination year, fiscal year before current fiscal year, finance receivable	24		24		32
Term loans by origination year, two years before current fiscal year, finance receivable	23		23		9
Term loans by origination year, three years before current fiscal year, finance receivable	4		4		1
Term loans by origination year, four years before current fiscal year, finance receivable	1		1		1
Term loans by origination year, more than five years before current fiscal year, finance receivable	2		2		2
Revolving loans, finance receivable	23		23		17
Revolving loans converted to term loans, finance receivable	4		4		6
Total loans	84		84		92
Other consumer [Member] | 90 days or more past due and still accruing [Member]
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, by Origination Year [Abstract]
Term loans by origination year, current fiscal year, finance receivable	1		1		9
Term loans by origination year, fiscal year before current fiscal year, finance receivable	10		10		14
Term loans by origination year, two years before current fiscal year, finance receivable	8		8		3
Term loans by origination year, three years before current fiscal year, finance receivable	2		2		1
Term loans by origination year, four years before current fiscal year, finance receivable	0		0		0
Term loans by origination year, more than five years before current fiscal year, finance receivable	1		1		1
Revolving loans, finance receivable	13		13		15
Revolving loans converted to term loans, finance receivable	12		12		13
Total loans	$ 47		$ 47		$ 56