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, 2020	Dec. 31, 2019	Dec. 31, 2018
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans sold	$ 492	$ 217	$ 158
Net gain associated with loan sales	3	2	2
Loans Purchased	63	300	37
Premium associated with loans purchased	0	11	0
Residential
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans Purchased	0	0	3
Home equity
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans Purchased	0	249	0
Other consumer
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans Purchased	63	51	34
Performing
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans sold	$ 492	$ 217	$ 158