Convertible Debt - Additional Information (Detail) (USD $)	1 Months Ended			3 Months Ended	9 Months Ended		0 Months Ended		9 Months Ended	1 Months Ended	3 Months Ended	0 Months Ended	1 Months Ended			3 Months Ended
	Jul. 31, 2012	Apr. 30, 2012	Nov. 30, 2011	Sep. 30, 2012	Sep. 30, 2012	Sep. 30, 2011	Jan. 09, 2012 Convertible Senior Notes 2011	Nov. 13, 2006 Convertible Senior Notes 2011	Sep. 30, 2012 Convertible Senior Notes 2013	Nov. 30, 2006 Convertible Senior Notes 2011 and 2013	Sep. 30, 2012 Convertible Senior Notes 2011 and 2013	Jan. 09, 2012 Purchased Options	Nov. 30, 2006 Purchased Options	Nov. 30, 2006 Sold Warrants	Nov. 13, 2006 Sold Warrants	Mar. 31, 2012 Exercised Warrants	Dec. 31, 2011 Group 1 Purchased Options	Dec. 31, 2011 Group 2 Purchased Options	Sep. 30, 2011 Convertible Senior Notes 2011 Convertible Senior Notes 2013	Dec. 31, 2010 Interest Rate Swap
Issuance date					Nov. 13, 2006
Senior Notes								$ 1,725,000,000	$ 1,725,000,000
Proceeds from issuance of senior unsecured obligations										3,450,000,000
Cash payment to noteholders for outstanding principal of converted Notes					1,699,816,000	0	1,699,800,000
Shares issued to noteholders for the excess of the conversion value over the principal amount of converted Notes							29,500,000
Value of the conversion value over the principal amount of converted Notes							661,400,000
Business day period									5 days
Trading-day period									5 days
Product of last reported sale price and the conversion rate									98.00%
Number of trading days									20 days
Trading day period during quarter									30 days
Ratio of stock price to conversion price									130.00%
Observation period									20 days
Debt Instrument, Convertible, Conversion Ratio, Principal Amount Basis									1,000
Conversion rate for the 2013 Notes will be 62.1978 shares of our common stock per one thousand dollars of principal amount of 2013 Notes									62.1978
Conversion premium									27.50%
Conversion price									$ 16.08
Amount of converted Notes									14,800,000
Convertible debt, carrying amount									1,636,900,000
Convertible debt, fair value				2,938,101,000	2,938,101,000				2,938,100,000
Carrying amount of the equity component									309,500,000
Debt Instrument, unamortized discount									73,300,000
Semi-annual interest rate								1.75%	1.75%
Debt Instrument, frequency of periodic payment									semi-annually
Effective interest rate											5.60%								5.60%
Incremental common shares attributable to call options and warrants													215,000,000	215,000,000
Aggregate amount paid for purchased options					69,905,000	0							669,100,000
Purchased options exercised																	107,500,000	107,500,000
Purchased options shares received												29,500,000
Common stock at an exercise price														$ 19.55	$ 19.55
Proceeds from issuance of warrants														391,100,000
Shares issues for exercised warrants																32,300,000
Conversion premium based on the closing price														55.00%
Closing price per share															$ 12.61
Aggregate notional amount of interest rate swap contracts designated as cash flow hedges																				900,000,000
Realized loss on replaced interest rate swap contracts	45,500,000	23,000,000	141,000,000
Accumulated realized losses in other comprehensive income related to previously-anticipated interest payments reclassified from other comprehensive income and recognized in the consolidated income statements				$ 39,500,000