Card Member Receivables and Card Member Loans (Details) - USD ($) $ in Millions	Sep. 30, 2021	Jun. 30, 2021	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Dec. 31, 2019
Card Member Receivables
Financing Receivable Segment [Abstract]
Financing receivables, gross	$ 13,618		$ 12,157
Less: Reserves for credit losses	10	$ (4)	70	$ 110	$ 184	$ 15
Financing receivables, net	13,608		12,087
Deferred discount revenue on card member receivable	19		19
Card Member Loans
Financing Receivable Segment [Abstract]
Less: Reserves for credit losses	23	$ 21	20	$ 22	$ 23	$ 17
Financing receivables, net	451		480
Global Consumer Services Group | Card Member Receivables
Financing Receivable Segment [Abstract]
Financing receivables, gross	2,271		2,157
Global Consumer Services Group | Card Member Loans
Financing Receivable Segment [Abstract]
Financing receivables, gross	474		500
Less: Reserves for credit losses	23		20
Financing receivables, net	451		480
Global Commercial Services | Card Member Receivables
Financing Receivable Segment [Abstract]
Financing receivables, gross	$ 11,347		$ 10,000