Intangible Assets (Narrative) (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Finite-Lived Intangible Assets [Line Items]
Document Period End Date			Sep. 30, 2017
Amortization expense relating to all intangible assets	$ 17	$ 15	$ 48	$ 48
Amortization expense for remainder of the year	14		$ 14
Document Fiscal Year Focus			2017
Intangible assets amortization expense, year one	47		$ 47
Intangible assets amortization expense, year two	41		41
Intangible assets amortization expense, year three	40		40
Intangible assets amortization expense, year four	30		30
Intangible assets amortization expense, year five	$ 24		$ 24