Mortgage Loans Held for Sale - Mortgage Loans Held for Sale (Details) - USD ($) $ in Millions	Sep. 30, 2021	Dec. 31, 2020
Accounts, Notes, Loans and Financing Receivable [Line Items]
Mortgage loans held for sale – UPB	$ 7,664	$ 5,438
Mark-to-market adjustment(1)	275	282
Total mortgage loans held for sale	7,939	5,720
Mortgage Loans Held for Sale, Nonaccrual Basis Unpaid Principal Balance	1,924	64
Fair Value, Mortgage Loans Held for Sale non-accrual status	2,002	54
Ginnie mae repurchased loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Mortgage Loans Held for Sale, Nonaccrual Basis Unpaid Principal Balance	$ 1,906	$ 48