MSR (Changes in the Servicing Assets) (Detail) - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2019	Mar. 31, 2018
Servicing Assets at Fair Value
Fair value at beginning of period		$ 938	$ 858
Servicing rights originated		24	16
Servicing rights acquired		0	24
Servicing rights obtained in acquisition		263	0
Changes in fair value due to changes in inputs or assumptions	[1]	(57)	57
Changes in fair value due to other changes in fair value	[2]	(27)	(29)
Fair value at end of period		$ 1,141	$ 926

[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 .