Intangible Assets (Narrative) (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Schedule Of Amortized And Unamortized Intangible Assets [Line Items]
Amortization expense relating to all intangible assets	$ 4	$ 1	$ 15	$ 2
Amortization expense for remainder of the year	5		5
Intangible assets amortization expense, year one	18		18
Intangible assets amortization expense, year two	18		18
Intangible assets amortization expense, year three	18		18
Intangible assets amortization expense, year four	18		18
Intangible assets amortization expense, year five	$ 18		$ 18