Unrecognized Tax Benefits (Detail) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Income Tax Disclosure [Abstract]
Unrecognized tax benefits, non-current income taxes payable	$ 46	$ 40
Unrecognized Tax Benefits, Interest on Income Taxes Accrued	$ 26	$ 29

Amount of interest expense accrued for an underpayment of income taxes.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 15
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=84230637&loc=d3e32718-109319

Name:	us-gaap_UnrecognizedTaxBenefitsInterestOnIncomeTaxesAccrued
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant