Senior Notes and Contingent Convertible Senior Notes Purchased (Parenthetical) (Detail) In Millions, unless otherwise specified	9 Months Ended												9 Months Ended
	Sep. 30, 2011 USD ($)	Sep. 30, 2012 7.625% Senior Notes Due 2013	Sep. 30, 2012 9.5% Senior Notes Due 2015	Sep. 30, 2012 6.25% Euro-Denominated Senior Notes Due 2017	Sep. 30, 2012 6.5% Senior Notes Due 2017	Sep. 30, 2012 6.875% Senior Notes Due 2018	Sep. 30, 2012 7.25% Senior Notes Due 2018	Sep. 30, 2012 6.625% Senior Notes Due 2020	Sep. 30, 2012 2.75% Contingent Convertible Senior Notes Due 2035	Sep. 30, 2012 2.5% Contingent Convertible Senior Notes Due 2037	Sep. 30, 2012 2.25% Contingent Convertible Senior Notes Due 2038	Dec. 31, 2011 2.25% Contingent Convertible Senior Notes Due 2038	Sep. 30, 2011 Euro-Denominated Senior Notes EUR (€)	Sep. 30, 2011 Senior Notes USD ($)	Sep. 30, 2011 Senior Notes 7.625% Senior Notes Due 2013 USD ($)	Sep. 30, 2011 Senior Notes 9.5% Senior Notes Due 2015 USD ($)	Sep. 30, 2011 Senior Notes 6.25% Euro-Denominated Senior Notes Due 2017 USD ($)		Sep. 30, 2011 Senior Notes 6.5% Senior Notes Due 2017 USD ($)	Sep. 30, 2011 Senior Notes 6.875% Senior Notes Due 2018 USD ($)	Sep. 30, 2011 Senior Notes 7.25% Senior Notes Due 2018 USD ($)	Sep. 30, 2011 Senior Notes 6.625% Senior Notes Due 2020 USD ($)	Sep. 30, 2011 Convertible Senior Notes USD ($)	Sep. 30, 2011 Convertible Senior Notes 2.75% Contingent Convertible Senior Notes Due 2035 USD ($)	Sep. 30, 2011 Convertible Senior Notes 2.5% Contingent Convertible Senior Notes Due 2037 USD ($)	Sep. 30, 2011 Convertible Senior Notes 2.25% Contingent Convertible Senior Notes Due 2038 USD ($)
Debt Instrument [Line Items]
Principal Amount Purchased	$ 1,904												€ 256	$ 1,373	$ 36	$ 160	$ 380	[1]	$ 440	$ 126	$ 131	$ 100	$ 531	$ 55	$ 210	$ 266
Foreign Currency Exchange Rate, Translation	1.4821
Interest rate		7.625%	9.50%	6.25%	6.50%	6.875%	7.25%	6.625%	2.75%	2.50%	2.25%
Debt instrument maturity period		2013	2015	2017	2017	2018	2018	2020	2035	2037	2038	2038

[1] We purchased €256 million in aggregate principal amount of our euro-denominated senior notes which had a value of $380 million based on the exchange rate of $1.4821 to €1.00. Simultaneously with our purchase of the euro-denominated senior notes, we unwound cross currency swaps for the same principal amount. See Note 7 for additional information.