Mortgage Servicing Rights and Related Liabilities - Narrative (Details) - USD ($) $ in Millions	Sep. 30, 2023	Dec. 31, 2022	Sep. 30, 2022
Servicing Asset at Amortized Cost [Line Items]
Excess spread financing - fair value	$ 446	$ 509
Forward MSRs Sold
Servicing Asset at Amortized Cost [Line Items]
UPB	23,789		$ 20,723
Forward MSRs Sold, Subservicing Retained
Servicing Asset at Amortized Cost [Line Items]
UPB	22,640		$ 19,692
Excess spread financing
Servicing Asset at Amortized Cost [Line Items]
UPB	$ 76,732	$ 83,706