Operating Lease Equipment (Additional Information) (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Operating Lease Equipment
Other Asset Impairment Charges			$ (18)	$ (9)	[1]
Operating lease equipment | Commercial Banking
Operating Lease Equipment
Other Asset Impairment Charges	$ 0	$ 6	$ 31	$ 11

[1] Net tax deficiencies of $ 6 were reclassified from capital surplus to applicable income tax expense for the nine months ended September 30, 2016, related to the early adoption of ASU 2016-09 during the fourth quarter of 2016, with an effective date of January 1, 2016.