Loan Servicing - Analysis of Activity in Residential MSRs (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Servicing Asset at Fair Value, Amount [Roll Forward]
MSRs, carrying value, beginning balance	$ 2,618
Change in fair value due to changes in valuation inputs or assumptions:
MSRs, carrying value, ending balance	2,150
Residential MSRs
Servicing Asset at Fair Value, Amount [Roll Forward]
MSRs, carrying value, beginning balance	2,371	$ 957
Other additions	178	15
Change in fair value due to changes in valuation inputs or assumptions:
Prepayment speeds	(522)	(55)
OAS	45	4
Servicing costs	0	0
Realization of expected net servicing cash flows, passage of time and other	(148)	(33)
MSRs, carrying value, ending balance	$ 1,924	$ 888