Allowance for Credit Losses and Reserve for Unfunded Lending Commitments - Allowance for Credit Losses and Reserve for Unfunded Lending Commitments Activity (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Allowance for Credit Losses [Roll Forward]
Financing Receivable, Allowance for Credit Loss, Beginning Balance	$ 11,430
Amounts expected to become due from (to) partners which reduced (increased) provision for credit losses	677	$ (823)
Balance at the end of the period	11,308
Other
Allowance for Credit Losses [Roll Forward]
Amounts expected to become due from (to) partners which reduced (increased) provision for credit losses	(6)	(2)
Allowance for credit losses
Allowance for Credit Losses [Roll Forward]
Financing Receivable, Allowance for Credit Loss, Beginning Balance	11,430	15,564
Charge-offs	(1,321)	(1,354)
Recoveries	554	614
Net charge-offs	(767)	(740)
Amounts expected to become due from (to) partners which reduced (increased) provision for credit losses	648	(813)
Allowance build (release) for credit losses	(119)	(1,553)
Other changes	(3)	6
Balance at the end of the period	11,308	14,017
Reserve for unfunded lending commitments
Allowance for Credit Losses [Roll Forward]
Financing Receivable, Allowance for Credit Loss, Beginning Balance	165	195
Amounts expected to become due from (to) partners which reduced (increased) provision for credit losses	35	(8)
Balance at the end of the period	200	187
Combined allowance and reserve
Allowance for Credit Losses [Roll Forward]
Balance at the end of the period	11,508	14,204
Credit Card | Allowance for credit losses
Allowance for Credit Losses [Roll Forward]
Financing Receivable, Allowance for Credit Loss, Beginning Balance	8,345	11,191
Charge-offs	(955)	(993)
Recoveries	348	360
Net charge-offs	(607)	(633)
Amounts expected to become due from (to) partners which reduced (increased) provision for credit losses	545	(492)
Allowance build (release) for credit losses	(62)	(1,125)
Other changes	(3)	6
Balance at the end of the period	8,280	10,072
Credit Card | Reserve for unfunded lending commitments
Allowance for Credit Losses [Roll Forward]
Financing Receivable, Allowance for Credit Loss, Beginning Balance	0	0
Amounts expected to become due from (to) partners which reduced (increased) provision for credit losses	0	0
Balance at the end of the period	0	0
Credit Card | Combined allowance and reserve
Allowance for Credit Losses [Roll Forward]
Balance at the end of the period	8,280	10,072
Consumer Banking | Allowance for credit losses
Allowance for Credit Losses [Roll Forward]
Financing Receivable, Allowance for Credit Loss, Beginning Balance	1,918	2,715
Charge-offs	(349)	(342)
Recoveries	203	251
Net charge-offs	(146)	(91)
Amounts expected to become due from (to) partners which reduced (increased) provision for credit losses	130	(126)
Allowance build (release) for credit losses	(16)	(217)
Other changes	0	0
Balance at the end of the period	1,902	2,498
Consumer Banking | Reserve for unfunded lending commitments
Allowance for Credit Losses [Roll Forward]
Financing Receivable, Allowance for Credit Loss, Beginning Balance	0	0
Amounts expected to become due from (to) partners which reduced (increased) provision for credit losses	0	0
Balance at the end of the period	0	0
Consumer Banking | Combined allowance and reserve
Allowance for Credit Losses [Roll Forward]
Balance at the end of the period	1,902	2,498
Commercial Banking | Allowance for credit losses
Allowance for Credit Losses [Roll Forward]
Financing Receivable, Allowance for Credit Loss, Beginning Balance	1,167	1,658
Charge-offs	(17)	(19)
Recoveries	3	3
Net charge-offs	(14)	(16)
Amounts expected to become due from (to) partners which reduced (increased) provision for credit losses	(27)	(195)
Allowance build (release) for credit losses	(41)	(211)
Other changes	0	0
Balance at the end of the period	1,126	1,447
Commercial Banking | Reserve for unfunded lending commitments
Allowance for Credit Losses [Roll Forward]
Financing Receivable, Allowance for Credit Loss, Beginning Balance	165	195
Amounts expected to become due from (to) partners which reduced (increased) provision for credit losses	35	(8)
Balance at the end of the period	200	187
Commercial Banking | Combined allowance and reserve
Allowance for Credit Losses [Roll Forward]
Balance at the end of the period	$ 1,326	$ 1,634