Debt - Key Components of Convertible Debt (Detail) (Convertible Senior Notes 2011 and 2013, USD $) In Millions, unless otherwise specified	12 Months Ended
Dec. 31, 2013	Dec. 31, 2012
Convertible Senior Notes 2011 and 2013
Debt Instrument [Line Items]
Contractual interest expense on the coupon	$ 27	$ 30
Amortization of the discount component recognized as interest expense	58	61
Total interest expense on the convertible debt	$ 85	$ 91

Amount of noncash expense included in interest expense to amortize debt discount and premium associated with the related debt instruments. Excludes amortization of financing costs. Alternate captions include noncash interest expense.

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- Definition

Total interest costs incurred during the period and either capitalized or charged against earnings.

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Amount of the cost of borrowed funds accounted for as interest expense for debt.

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