Asset Quality - Summary of Post-Modification Outstanding Recorded Investment TDRs (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Financing Receivables, Modifications, Rollforward [Roll Forward]
Balance at beginning of the period	$ 376	$ 340	$ 363	$ 347
Additions	22	22	81	39
Payments	(60)	(35)	(81)	(53)
Charge-offs	(4)	(17)	(29)	(23)
Balance at end of period	$ 334	$ 310	$ 334	$ 310