Loan Servicing - Analysis of Activity in Residential MSRs (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Servicing Asset at Fair Value, Amount [Roll Forward]
MSRs, carrying value, beginning balance	$ 1,108
Change in fair value due to changes in valuation inputs or assumptions:
MSRs, carrying value, ending balance	1,036
Residential MSRs
Servicing Asset at Fair Value, Amount [Roll Forward]
MSRs, carrying value, beginning balance	957	$ 914
Additions	15	28
Change in fair value due to changes in valuation inputs or assumptions:
Prepayment speeds	(55)	61
OAS	4	2
Servicing costs	0	0
Realization of expected net servicing cash flows, passage of time and other	(33)	(32)
MSRs, carrying value, ending balance	888	973
Gains (losses) on derivative financial instruments used to mitigate the income statement effect of changes in residential MSR fair value	$ 52	$ (63)