Mortgage Servicing Assets - Schedule of Changes in Carrying Amount of Mortgage Servicing Assets (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Commercial Mortgage Backed Securities
Servicing Asset at Amortized Cost, Balance [Roll Forward]
Balance at beginning of period	$ 627	$ 647	$ 653	$ 634
Servicing retained from loan sales	40	26	66	78
Purchases	8	9	18	32
Amortization	(30)	(31)	(92)	(93)
Temporary (impairments) recoveries	0	0	0	0
Balance at end of period	645	651	645	651
Fair value at end of period	871	942	871	942
Agency residential mortgage-backed securities
Servicing Asset at Amortized Cost, Balance [Roll Forward]
Balance at beginning of period	106	104	106	93
Servicing retained from loan sales	4	4	8	21
Purchases	0	0	0	0
Amortization	(3)	(3)	(7)	(10)
Temporary (impairments) recoveries	0	0	0	1
Balance at end of period	107	105	107	105
Fair value at end of period	$ 137	$ 127	$ 137	$ 127