Intangible Assets (Narrative) (Detail) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Finite-Lived Intangible Assets [Line Items]
Document Period End Date			Jun. 30, 2018
Amortization expense relating to all intangible assets	$ 19	$ 16	$ 33	$ 31
Amortization expense for remainder of the year	37		$ 37
Document Fiscal Year Focus			2018
Intangible assets amortization expense, year one	50		$ 50
Intangible assets amortization expense, year two	43		43
Intangible assets amortization expense, year three	30		30
Intangible assets amortization expense, year four	24		24
Intangible assets amortization expense, year five	$ 21		$ 21