Loans Held-for-Investment - UPB of Loan Sales and Purchases in the Loans Held-for-Investment Portfolio (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Accounts, Notes, Loans and Financing Receivable [Line Items]
Net gain associated with loan sales	$ 2	$ 2
Loans purchased	300	37	$ 258
Premium associated with loans purchased	11	0	9
Residential first mortgage loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans sold	217	158	127
Net gain associated with loan sales			2
Loans purchased			8
HELOC
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans purchased			250
Other consumer
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans purchased			0
Performing loans | Residential first mortgage loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans sold			102
Nonperforming loans | Residential first mortgage loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans sold			$ 25
Performing loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans sold	217	158
Residential first mortgage loans | Nonperforming loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans sold	0	0
Other consumer | Residential first mortgage loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans purchased	0	3
Other consumer | HELOC
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans purchased	249	0
Other consumer | Other consumer
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans purchased	$ 51	$ 34