Mortgage Servicing Rights and Related Liabilities - Reverse MSRs and Liabilities - Amortized Cost (Details) - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019
Servicing Asset at Amortized Cost, Balance [Roll Forward]
Fair value - end of period	$ 2,757	$ 3,505
Servicing Liability at Amortized Cost [Roll Forward]
Balance - beginning of period	61
Balance - end of the period	48
Assets
Servicing Asset at Amortized Cost, Balance [Roll Forward]
Balance - beginning of period	6	11
Amortization/accretion	0	(1)
Servicing asset, adjustments	0	(4)
Balance - end of the period	6	6
Fair value - end of period	6	7
Liabilities
Servicing Liability at Amortized Cost [Roll Forward]
Balance - beginning of period	61	71
Amortization/accretion	(13)	(28)
Servicing liability, adjustments	0	37
Balance - end of the period	48	80
Fair value - end of period	$ 12	$ 44