Reserves for Losses (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Reserve for Losses [Roll Forward]
Balance, January 1			$ 2,134	$ 1,706
Provisions	$ 604	$ 560	1,732	1,587
Net write-offs Principal, interest and fees			(389)	(330)
Other			10	9
Ending Balance	$ 2,232	$ 1,937	2,232	1,937
Net Write Offs [Member]
Reserve for Losses [Roll Forward]
Provisions			1,732	1,587
Principal [Member]
Reserve for Losses [Roll Forward]
Net write-offs Principal, interest and fees			(1,367)	(1,140)
Interest and Fees [Member]
Reserve for Losses [Roll Forward]
Net write-offs Principal, interest and fees			(277)	(225)
Troubled Debt Restructuring [Member]
Reserve for Losses [Roll Forward]
Net write-offs Principal, interest and fees			(53)	(21)
Foreign Currency Translation Adjustments [Member]
Reserve for Losses [Roll Forward]
Other			(3)	(4)
Other Items [Member]
Reserve for Losses [Roll Forward]
Other			$ 13	$ 13