Loan Servicing - Analysis of Activity in Residential MSRs (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015
Servicing Asset at Fair Value, Amount [Roll Forward]
MSRs, carrying value, beginning of period	$ 880
Change in fair value due to changes in valuation inputs or assumptions:
MSRs, carrying value, end of period	828
Gains (losses) on derivative financial instruments used to mitigate the income statement effect of changes in MSR fair value	232	$ 56
Residential Mortgage
Servicing Asset at Fair Value, Amount [Roll Forward]
MSRs, carrying value, beginning of period	880	844
Additions	99	125
Change in fair value due to changes in valuation inputs or assumptions:
Prepayment speeds	(180)	76
OAS	9	(67)
Servicing Costs	2	(25)
Realization of expected net servicing cash flows, passage of time and other	(103)	(105)
MSRs, carrying value, end of period	$ 707	$ 848