Intangible Assets (Narrative) (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Finite-Lived Intangible Assets [Line Items]
Amortization expense relating to all intangible assets	$ 7	$ 4	$ 12	$ 10
Amortization expense for remainder of the year	14		14
Intangible assets amortization expense, year one	28		28
Intangible assets amortization expense, year two	28		28
Intangible assets amortization expense, year three	28		28
Intangible assets amortization expense, year four	28		28
Intangible assets amortization expense, year five	$ 28		$ 28