MSR (Changes in the Servicing Assets) (Detail) - USD ($) $ in Millions		9 Months Ended
		Sep. 30, 2018	Sep. 30, 2017
Servicing Assets at Fair Value
Fair value at beginning of period		$ 858	$ 744
Servicing rights originated		62	99
Servicing rights acquired		82	109
Changes in fair value due to changes in inputs or assumptions	[1]	103	(15)
Changes in fair value due to other changes in fair value	[2]	(95)	(89)
Fair value at end of period		$ 1,010	$ 848

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

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