Accounting and Reporting Developments (Additional Information) (Detail) $ in Millions	3 Months Ended	9 Months Ended
	Sep. 30, 2018 USD ($)	Sep. 30, 2018 USD ($)
Accounting Policies [Abstract]
Deferred gains on sale-leaseback transactions	$ 14	$ 14
Reduction to card and processing revenue	33	93
Lower limit, right of use asset and lease liabilities	400	400
Upper limit, right of use asset and lease liabilities	$ 500	$ 500