Mortgage Servicing Assets - Changes in Carrying Amount of Mortgage Servicing Assets (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Commercial Mortgage Backed Securities
Servicing Asset at Amortized Cost, Balance [Roll Forward]
Balance at beginning of period	$ 644	$ 588	$ 634	$ 578
Servicing retained from loan sales	22	28	52	57
Purchases	12	7	23	14
Amortization	(31)	(30)	(62)	(59)
Temporary (impairments) recoveries	0	7	0	10
Balance at end of period	647	600	647	600
Fair value at end of period	938	704	938	704
Agency residential mortgage-backed securities
Servicing Asset at Amortized Cost, Balance [Roll Forward]
Balance at beginning of period	101	72	93	58
Servicing retained from loan sales	6	12	17	23
Purchases	0	0	0	0
Amortization	(3)	(5)	(7)	(10)
Temporary (impairments) recoveries	0	(2)	1	6
Balance at end of period	104	77	104	77
Fair value at end of period	$ 125	$ 81	$ 125	$ 81