Loan Receivables (Schedule of Net Charge-offs of Interest and Fee Revenues on Loan Receivables) (Details) - USD ($) $ in Millions	3 Months Ended
Mar. 31, 2020	Mar. 31, 2019
Receivables [Abstract]
Interest and fees accrued subsequently charged off, net of recoveries (recorded as a reduction of interest income)	$ 143	$ 127
Fees accrued subsequently charged off, net of recoveries (recorded as a reduction to other income)	$ 35	$ 31

Interest and fees accrued subsequently charged off, net of recoveries (recorded as a reduction of interest income).

No definition available.

Name:	dfs_InterestAndFeesAccruedSubsequentlyChargedOffNetOfRecoveries
Namespace Prefix:	dfs_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration