Intangible Assets (Narrative) (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Finite-Lived Intangible Assets [Line Items]
Amortization expense relating to all intangible assets	$ 7	$ 4	$ 20	$ 15
Amortization expense for remainder of the year	7		7
Intangible assets amortization expense, year one	29		29
Intangible assets amortization expense, year two	29		29
Intangible assets amortization expense, year three	29		29
Intangible assets amortization expense, year four	29		29
Intangible assets amortization expense, year five	$ 29		$ 29