Benefit Plans - Amounts Recognized in the Consolidated Balance Sheets (Detail) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Pension Benefits [Member]
Amounts recognized in the Consolidated Balance Sheets consist of:
Other assets	$ 9	$ 4
Other liabilities	(624)	(669)
Net amount recognized	(615)	(665)
Other Postretirement Benefits [Member]
Amounts recognized in the Consolidated Balance Sheets consist of:
Other assets	49	47
Other liabilities	(17)	(21)
Net amount recognized	$ 32	$ 26

Amount of asset, recognized in statement of financial position, for overfunded defined benefit pension and other postretirement plans.

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Name:	us-gaap_DefinedBenefitPlanAssetsForPlanBenefitsNoncurrent
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant