Mortgage Servicing Rights and Related Liabilities - Amortized Cost of Reverse MSRs and Liabilities (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Servicing Asset at Amortized Cost, Balance [Roll Forward]
Fair value - end of year	$ 2,703	$ 3,496
Servicing Liability at Amortized Cost [Roll Forward]
Balance - beginning of year	61
Balance - end of year	41	61
Reverse Mortgage Servicing Rights
Servicing Asset at Amortized Cost, Balance [Roll Forward]
Balance - beginning of year	6	11
Amortization/accretion	(1)	(1)
Adjustments	0	(4)
Balance - end of year	5	6
Fair value - end of year	6	6
Mortgage Servicing Right Liability
Servicing Liability at Amortized Cost [Roll Forward]
Balance - beginning of year	61	71
Amortization/accretion	(20)	(47)
Adjustments	0	37
Balance - end of year	41	61
Fair value - end of year	$ 37	$ 28