Loans and Related Allowance for Credit Losses, Credit Quality Indicators for Credit Card Loans (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
Credit card [Member]
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, by Origination Year [Abstract]
Revolving loans, finance receivable	51,559		51,805
Revolving loans converted to term loans, finance receivable	476		425
Total loans	52,035		52,230
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss, Writeoff, by Origination Year [Abstract]
Revolving loans, charge-offs	627		1,909
Revolving loans converted to term loans, charge-offs	37		100
Loan charge-offs, loans	664	$ 424	2,009
Credit card [Member] | FICO 740 or more [Member]
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, by Origination Year [Abstract]
Revolving loans, finance receivable	19,442		19,153
Revolving loans converted to term loans, finance receivable	24		21
Total loans	19,466		19,174
Credit card [Member] | FICO 700 to 739 [Member]
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, by Origination Year [Abstract]
Revolving loans, finance receivable	11,612		11,727
Revolving loans converted to term loans, finance receivable	57		51
Total loans	11,669		11,778
Credit card [Member] | FICO 660 to 699 [Member]
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, by Origination Year [Abstract]
Revolving loans, finance receivable	10,341		10,592
Revolving loans converted to term loans, finance receivable	93		84
Total loans	10,434		10,676
Credit card [Member] | FICO 620 to 659 [Member]
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, by Origination Year [Abstract]
Revolving loans, finance receivable	5,047		5,273
Revolving loans converted to term loans, finance receivable	85		76
Total loans	5,132		5,349
Credit card [Member] | FICO less than 620 [Member]
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, by Origination Year [Abstract]
Revolving loans, finance receivable	4,923		4,861
Revolving loans converted to term loans, finance receivable	215		192
Total loans	5,138		5,053
Credit card [Member] | No FICO available [Member]
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, by Origination Year [Abstract]
Revolving loans, finance receivable	194		199
Revolving loans converted to term loans, finance receivable	2		1
Total loans	196		200
Credit card [Member] | Current-29 days past due [Member]
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, by Origination Year [Abstract]
Revolving loans, finance receivable	50,141		50,428
Revolving loans converted to term loans, finance receivable	392		350
Total loans	50,533		50,778
Credit card [Member] | 30 to 89 days past due [Member]
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, by Origination Year [Abstract]
Revolving loans, finance receivable	638		660
Revolving loans converted to term loans, finance receivable	51		49
Total loans	689		709
Credit card [Member] | 90 days or more past due [Member]
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, by Origination Year [Abstract]
Revolving loans, finance receivable	780		717
Revolving loans converted to term loans, finance receivable	33		26
Total loans	$ 813		$ 743