Fair Value Measurements - Narrative (Details) - USD ($) $ in Millions	3 Months Ended	6 Months Ended	12 Months Ended
	Jun. 30, 2019	Jun. 30, 2019	Dec. 31, 2018
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Settlement liability	$ 2	$ 2	$ 2
DOJ Agreement
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair value adjustment on settlement liability	25	25
Settlement liability	$ 35	$ 35
Measurement Input, Expected Term | Level 3 | Residential Mortgage Servicing Rights Capitalized
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Weighted average life		4 years 1 month 6 days	5 years 2 months 12 days