Asset Quality - Summary of Post-Modification Outstanding Recorded Investment TDRs (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Financing Receivables, Modifications, Rollforward [Roll Forward]
Balance at beginning of the period	$ 334	$ 310	$ 363	$ 347
Additions	17	26	98	65
Payments	(81)	(22)	(162)	(75)
Charge-offs	0	(8)	(29)	(31)
Balance at end of period	$ 270	$ 306	$ 270	$ 306