MSR (Changes in the Servicing Assets) (Detail) - USD ($)		12 Months Ended
		Dec. 31, 2018	Dec. 31, 2017
Servicing Assets at Fair Value
Fair value at beginning of period		$ 858,000,000	$ 744,000,000
Servicing rights originated		81,000,000	127,000,000
Servicing rights acquired		82,000,000	109,000,000
Changes in fair value due to changes in inputs or assumptions	[1]	42,000,000	(1,000,000)
Changes in fair value due to other changes in fair value	[2]	(125,000,000)	(121,000,000)
Fair value at end of period		$ 938,000,000	$ 858,000,000

[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.