Asset Quality - Summary of Post-Modification Outstanding Recorded Investment TDRs (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Financing Receivables, Modifications, Rollforward [Roll Forward]
Balance at beginning of the period	$ 310	$ 395	$ 347	$ 399
Additions	26	20	65	88
Payments	(22)	(65)	(75)	(123)
Charge-offs	(8)	(3)	(31)	(17)
Balance at end of period	$ 306	$ 347	$ 306	$ 347