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		12 Months Ended
	Mar. 31, 2024	Mar. 31, 2023	Dec. 31, 2023
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, by Origination Year [Abstract]
Total loans	$ 384,456		$ 389,255
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss, Writeoff, by Origination Year [Abstract]
Loan charge-offs, loans	1,021	$ 774
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	576		3,306
Term loans by origination year, fiscal year before current fiscal year, finance receivable	2,862		2,178
Term loans by origination year, two years before current fiscal year, finance receivable	1,881		583
Term loans by origination year, three years before current fiscal year, finance receivable	483		169
Term loans by origination year, four years before current fiscal year, finance receivable	146		94
Term loans by origination year, more than five years before current fiscal year, finance receivable	124		64
Revolving loans, finance receivable	22,389		22,020
Revolving loans converted to term loans, finance receivable	136		125
Total loans	28,597		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	13		178
Term loans by origination year, fiscal year before current fiscal year, charge-offs	60		158
Term loans by origination year, two years before current fiscal year, charge-offs	39		52
Term loans by origination year, three years before current fiscal year, charge-offs	11		9
Term loans by origination year, four years before current fiscal year, charge-offs	2		9
Term loans by origination year, more than five years before current fiscal year, charge-offs	2		6
Revolving loans, charge-offs	17		62
Revolving loans converted to term loans, charge-offs	3		11
Loan charge-offs, loans	147	$ 105	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	450		1,911
Term loans by origination year, fiscal year before current fiscal year, finance receivable	1,576		926
Term loans by origination year, two years before current fiscal year, finance receivable	786		265
Term loans by origination year, three years before current fiscal year, finance receivable	209		85
Term loans by origination year, four years before current fiscal year, finance receivable	76		36
Term loans by origination year, more than five years before current fiscal year, finance receivable	49		28
Revolving loans, finance receivable	1,042		1,152
Revolving loans converted to term loans, finance receivable	34		27
Total loans	4,222		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	77		642
Term loans by origination year, fiscal year before current fiscal year, finance receivable	559		409
Term loans by origination year, two years before current fiscal year, finance receivable	347		107
Term loans by origination year, three years before current fiscal year, finance receivable	89		27
Term loans by origination year, four years before current fiscal year, finance receivable	20		14
Term loans by origination year, more than five years before current fiscal year, finance receivable	19		10
Revolving loans, finance receivable	481		507
Revolving loans converted to term loans, finance receivable	16		16
Total loans	1,608		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	21		403
Term loans by origination year, fiscal year before current fiscal year, finance receivable	380		365
Term loans by origination year, two years before current fiscal year, finance receivable	307		93
Term loans by origination year, three years before current fiscal year, finance receivable	84		16
Term loans by origination year, four years before current fiscal year, finance receivable	13		11
Term loans by origination year, more than five years before current fiscal year, finance receivable	15		8
Revolving loans, finance receivable	362		395
Revolving loans converted to term loans, finance receivable	16		16
Total loans	1,198		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	2		129
Term loans by origination year, fiscal year before current fiscal year, finance receivable	128		166
Term loans by origination year, two years before current fiscal year, finance receivable	139		45
Term loans by origination year, three years before current fiscal year, finance receivable	35		6
Term loans by origination year, four years before current fiscal year, finance receivable	5		6
Term loans by origination year, more than five years before current fiscal year, finance receivable	8		5
Revolving loans, finance receivable	139		147
Revolving loans converted to term loans, finance receivable	10		11
Total loans	466		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	1		75
Term loans by origination year, fiscal year before current fiscal year, finance receivable	98		152
Term loans by origination year, two years before current fiscal year, finance receivable	149		49
Term loans by origination year, three years before current fiscal year, finance receivable	44		8
Term loans by origination year, four years before current fiscal year, finance receivable	6		8
Term loans by origination year, more than five years before current fiscal year, finance receivable	11		6
Revolving loans, finance receivable	150		152
Revolving loans converted to term loans, finance receivable	18		17
Total loans	477		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	25		146
Term loans by origination year, fiscal year before current fiscal year, finance receivable	121		160
Term loans by origination year, two years before current fiscal year, finance receivable	153		24
Term loans by origination year, three years before current fiscal year, finance receivable	22		27
Term loans by origination year, four years before current fiscal year, finance receivable	26		19
Term loans by origination year, more than five years before current fiscal year, finance receivable	22		7
Revolving loans, finance receivable	20,215		19,667
Revolving loans converted to term loans, finance receivable	42		38
Total loans	20,626		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	576		3,273
Term loans by origination year, fiscal year before current fiscal year, finance receivable	2,825		2,132
Term loans by origination year, two years before current fiscal year, finance receivable	1,843		571
Term loans by origination year, three years before current fiscal year, finance receivable	473		167
Term loans by origination year, four years before current fiscal year, finance receivable	145		93
Term loans by origination year, more than five years before current fiscal year, finance receivable	120		61
Revolving loans, finance receivable	22,359		21,988
Revolving loans converted to term loans, finance receivable	116		106
Total loans	28,457		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	0		24
Term loans by origination year, fiscal year before current fiscal year, finance receivable	25		32
Term loans by origination year, two years before current fiscal year, finance receivable	25		9
Term loans by origination year, three years before current fiscal year, finance receivable	7		1
Term loans by origination year, four years before current fiscal year, finance receivable	1		1
Term loans by origination year, more than five years before current fiscal year, finance receivable	3		2
Revolving loans, finance receivable	15		17
Revolving loans converted to term loans, finance receivable	7		6
Total loans	83		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	0		9
Term loans by origination year, fiscal year before current fiscal year, finance receivable	12		14
Term loans by origination year, two years before current fiscal year, finance receivable	13		3
Term loans by origination year, three years before current fiscal year, finance receivable	3		1
Term loans by origination year, four years before current fiscal year, finance receivable	0		0
Term loans by origination year, more than five years before current fiscal year, finance receivable	1		1
Revolving loans, finance receivable	15		15
Revolving loans converted to term loans, finance receivable	13		13
Total loans	$ 57		$ 56