Asset Quality - Summary of Post-Modification Outstanding Recorded Investment TDRs (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Financing Receivables, Modifications, Rollforward [Roll Forward]
Balance at beginning of the period	$ 340	$ 365	$ 347	$ 399
Additions	22	54	39	68
Payments	(35)	(19)	(53)	(58)
Charge-offs	(17)	(5)	(23)	(14)
Balance at end of period	$ 310	$ 395	$ 310	$ 395