Mortgage Servicing Assets - Narrative (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022
Commercial Mortgage Backed Securities
Servicing Assets at Fair Value [Line Items]
Contractual fee income from servicing commercial mortgage loans	$ 234	$ 219
Amortization of servicing commercial mortgage loans	92	93
Residential mortgage-backed securities
Servicing Assets at Fair Value [Line Items]
Contractual fee income from servicing commercial mortgage loans	25	27
Amortization of servicing commercial mortgage loans	$ 7	$ 10