Significant Accounting Policies - Narrative (Details) - USD ($) $ in Millions	5 Months Ended	7 Months Ended	12 Months Ended
	Dec. 31, 2018	Jul. 31, 2018	Dec. 31, 2020	Dec. 31, 2019
Derivative [Line Items]
Mortgage loan sale period			30 days
Advertising costs	$ 17	$ 33	$ 38	$ 33
Mortgage Servicing Rights Financing
Derivative [Line Items]
Mortgage servicing rights financing - fair value			$ 33	$ 37
Minimum
Derivative [Line Items]
Loan commitment period			30 days
Maximum
Derivative [Line Items]
Loan commitment period			90 days