MSR (Changes in the Servicing Assets) (Detail) - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017
Servicing Assets at Fair Value
Fair value at beginning of period	$ 858	$ 744
Servicing rights originated	35	66
Servicing rights acquired	50	109
Changes in fair value due to changes in inputs or assumptions	78	(13)	[1]
Changes in fair value due to other changes in fair value	(62)	(57)	[2]
Fair value at end of period	$ 959	$ 849

[1] Primarily reflects changes in prepayment speed and OAS spread assumptions which are updated based on market interest rates

[2] Pr imarily reflects changes due to collection of contractual cash flows and the passage of time