Reserves for Losses Textuals (Details) - USD ($) $ in Millions	9 Months Ended
Sep. 30, 2019	Sep. 30, 2018
Reserves for Losses [Abstract]
Participation interests in Card Member receivables purchased from affiliates	$ 2,700.0	$ 9,700.0
Allowance for Card Member receivables, recoveries of bad debts	94.0	84.0
Participation interests in Card Member receivables sold	$ 1,100.0	$ 4,500.0

Amount of increase in allowance for credit loss on accounts receivable, from recovery.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 20
-Section 50
-Paragraph 13
-Subparagraph (e)
-URI http://asc.fasb.org/extlink&oid=119407570&loc=SL82919249-210447

Name:	us-gaap_AllowanceForDoubtfulAccountsReceivableRecoveries
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration