Loans and Card Member Receivables (Details 3) - USD ($) $ in Millions	Sep. 30, 2021	Dec. 31, 2020
Impaired loans and receivables
Loans over 90 days past due and accruing interest	$ 149	$ 226
Non-accrual loans	92	176
Loans and receivables modified as a Troubled Debt Restructuring in Program	1,543	3,086
Loans and receivables modified as Troubled Debt Restructuring Out of Program	1,559	430
Total impaired loans and receivables	3,343	3,918
Reserve for Credit Losses - TDRs	735	1,346
Accounts Receivable and Loans Textuals
Total loans and receivables modified as a TDR, past due 90 days and still accruing	32	32
Total loans and receivables modified as a TDR, non-accrual	17	11
Out of Program TDR accounts that completed modification programs	1,413	316
Out of Program TDR accounts not in compliance with modification programs	146	114
Other Loans
Impaired loans and receivables
Loans over 90 days past due and accruing interest	1	2
Non-accrual loans	0	1
Loans and receivables modified as a Troubled Debt Restructuring in Program	97	248
Loans and receivables modified as Troubled Debt Restructuring Out of Program	3	6
Total impaired loans and receivables	101	257
Reserve for Credit Losses - TDRs	9	80
GCSG | Card Member Loans
Impaired loans and receivables
Loans over 90 days past due and accruing interest	134	203
Non-accrual loans	77	146
Loans and receivables modified as a Troubled Debt Restructuring in Program	845	1,586
Loans and receivables modified as Troubled Debt Restructuring Out of Program	891	248
Total impaired loans and receivables	1,947	2,183
Reserve for Credit Losses - TDRs	491	782
GCSG | Card Member Receivables
Impaired loans and receivables
Loans over 90 days past due and accruing interest	0	0
Non-accrual loans	0	0
Loans and receivables modified as a Troubled Debt Restructuring in Program	138	240
Loans and receivables modified as Troubled Debt Restructuring Out of Program	101	34
Total impaired loans and receivables	239	274
Reserve for Credit Losses - TDRs	24	60
GCS | Card Member Loans
Impaired loans and receivables
Loans over 90 days past due and accruing interest	14	21
Non-accrual loans	15	29
Loans and receivables modified as a Troubled Debt Restructuring in Program	209	478
Loans and receivables modified as Troubled Debt Restructuring Out of Program	299	67
Total impaired loans and receivables	537	595
Reserve for Credit Losses - TDRs	165	285
GCS | Card Member Receivables
Impaired loans and receivables
Loans over 90 days past due and accruing interest	0	0
Non-accrual loans	0	0
Loans and receivables modified as a Troubled Debt Restructuring in Program	254	534
Loans and receivables modified as Troubled Debt Restructuring Out of Program	265	75
Total impaired loans and receivables	519	609
Reserve for Credit Losses - TDRs	$ 46	$ 139