Fair Value Measurements - Narrative (Details) - USD ($) $ in Millions	9 Months Ended	12 Months Ended
	Sep. 30, 2020	Dec. 31, 2019
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Settlement liability	$ 7	$ 3
DOJ Agreement
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value adjustment on settlement liability		25
Settlement liability		$ 35
Residential mortgage servicing rights capitalized | Measurement input, expected term | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Weighted average life	3 years 10 months 24 days	4 years 1 month 6 days