Loan Servicing - Analysis of Activity in Residential MSRs (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Servicing Asset at Fair Value, Amount [Roll Forward]
MSRs, carrying value, beginning balance	$ 1,056
Change in fair value due to changes in valuation inputs or assumptions:
MSRs, carrying value, ending balance	1,108	$ 1,056
Residential MSRs
Servicing Asset at Fair Value, Amount [Roll Forward]
MSRs, carrying value, beginning balance	914	915	$ 880
Additions	116	123	146
Change in fair value due to changes in valuation inputs or assumptions:
Prepayment speeds	(12)	(42)	13
OAS	57	46	10
Servicing costs	22	9	2
Realization of expected net servicing cash flows, passage of time and other	(140)	(137)	(136)
MSRs, carrying value, ending balance	957	914	915
Gains (losses) on derivative financial instruments used to mitigate the income statement effect of changes in residential MSR fair value	$ (63)	$ 0	$ 32