Mortgage Servicing Rights and Related Liabilities - Reverse MSRs and Liabilities - Amortized Cost (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019
Servicing Asset at Amortized Cost, Balance [Roll Forward]
Fair value - end of period	$ 2,663
Servicing Liability at Amortized Cost [Roll Forward]
Balance - beginning of period	61
Balance - end of the period	44
Assets
Servicing Asset at Amortized Cost, Balance [Roll Forward]
Balance - beginning of period	6	$ 11
Amortization/accretion	0	2
Servicing asset, adjustments	0	(6)
Balance - end of the period	6	7
Fair value - end of period	6	7
Mortgage servicing rights financing
Servicing Liability at Amortized Cost [Roll Forward]
Balance - beginning of period	61	71
Amortization/accretion	(17)	(39)
Servicing liability, adjustments	0	37
Balance - end of the period	44	69
Fair value - end of period	$ 7	$ 41