Pension Plans, Postretirement and Other Employee Benefits - Changes in Fair Value of Level 3 Assets (Detail) - Foreign - Fair Value, Inputs, Level 3 - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2017	Dec. 31, 2016
Schedule of Defined Benefit Plan Asset Allocation Targets [Line Items]
Balance at December 31 of the previous year	$ 9	$ 8
Relating to assets still held at the reporting date	0	1
Ending Balance at December 31	$ 9	$ 9

Amount, measured using unobservable inputs, of increase (decrease) in plan assets of defined benefit plan from actual return (loss) on assets still held.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (d)(5)(iv)(02)(A)
-URI http://asc.fasb.org/extlink&oid=82843861&loc=d3e1928-114920

Name:	us-gaap_DefinedBenefitPlanActualReturnOnPlanAssetsStillHeld
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration