Derivatives - Summary of gains (losses) for derivative instruments (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Derivatives
Net derivative gain related to mortgage servicing rights		$ (4)		$ 139
Gain on loans held for sale, net | Interest rate lock commitments
Derivatives
Gains on derivative instruments	$ 62	100	$ 175	278
Gain on loans held for sale, net | Forward delivery commitments
Derivatives
Gains on derivative instruments	$ (6)	(6)	(11)	(41)
Gain on loans held for sale, net | Option contracts
Derivatives
Gains on derivative instruments			$ (1)	(1)
Loan servicing income, net | MSR-related agreements
Derivatives
Net derivative gain related to mortgage servicing rights		$ (4)		$ 139