Loan Servicing - Analysis of Activity in Residential MSRs (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Servicing Asset at Fair Value, Amount [Roll Forward]
Residential MSRs, carrying value, beginning of period	$ 880
Change in fair value due to changes in valuation inputs or assumptions:
Residential MSRs, carrying value, end of period	860
Gains (losses) on derivative financial instruments used to mitigate the income statement effect of changes in fair value	143	$ 81
Residential Mortgage
Servicing Asset at Fair Value, Amount [Roll Forward]
Residential MSRs, carrying value, beginning of period	880	844
Additions	22	26
Change in fair value due to changes in valuation inputs or assumptions:
Prepayment speeds	(136)	(76)
OAS	9	5
Realization of expected net servicing cash flows, passage of time and other	(32)	(35)
Residential MSRs, carrying value, end of period	$ 743	$ 764