Loan Servicing - Analysis of Activity in Residential MSRs (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2020	Sep. 30, 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	1,991
Residential MSRs
Servicing Asset at Fair Value, Amount [Roll Forward]
MSRs, carrying value, beginning balance	2,371	$ 957
Additions	490	101
Change in fair value due to changes in valuation inputs or assumptions:
Prepayment speeds	(612)	(213)
OAS	53	36
Realization of expected net servicing cash flows, passage of time and other	(539)	(105)
MSRs, carrying value, ending balance	$ 1,763	$ 776