Debt - Additional Information (Detail) (USD $) Share data in Millions, except Per Share data, unless otherwise specified	0 Months Ended	1 Months Ended			1 Months Ended	3 Months Ended	9 Months Ended	0 Months Ended	1 Months Ended		1 Months Ended			1 Months Ended	3 Months Ended	9 Months Ended		3 Months Ended
	Jan. 07, 2014 Convertible Senior Notes 2013	Nov. 30, 2006 Convertible Senior Notes 2013	Jan. 07, 2013 Convertible Senior Notes 2013	Nov. 13, 2006 Convertible Senior Notes 2013	Nov. 30, 2006 Convertible Senior Notes 2011 and 2013	Sep. 30, 2013 Convertible Senior Notes 2011 and 2013	Sep. 30, 2013 Convertible Senior Notes 2011 and 2013	Jan. 07, 2014 Purchased Options	Nov. 30, 2006 Purchased Options	Dec. 31, 2013 Purchased Options	Nov. 30, 2006 Sold Warrants	Nov. 13, 2006 Sold Warrants	Mar. 17, 2014 Warrant	Mar. 17, 2014 Exercised Warrants	Sep. 30, 2014 Long-term Debt	Sep. 30, 2014 Long-term Debt	Jun. 30, 2013 Long-term Debt	Sep. 30, 2014 Interest Rate Swap	Jun. 30, 2012 Interest Rate Swap	Dec. 31, 2010 Interest Rate Swap
Long term debt, aggregate principal																	$ 5,500,000,000
Unamortized discount															6,000,000	6,000,000
Effective interest rate						5.60%	5.60%								2.54%	2.54%
Senior Notes				1,725,000,000
Stated interest rate				1.75%
Proceeds from issuance of senior unsecured obligations					3,500,000,000
Cash payment to noteholders for outstanding principal of converted Notes	1,700,000,000
Shares issued to noteholders for the excess of the conversion value over the principal amount of converted Notes (in shares)	35
Value of the conversion value over the principal amount of converted Notes	858,000,000
Observation period	20 days
Convertible conversion ratio	0.0626978
Conversion premium	26.50%
Conversion price per share			$ 15.95
Debt Instrument, frequency of periodic payment		semi-annually
Incremental common shares attributable to call options and warrants									215		215
Aggregate amount paid for purchased options									669,000,000
Purchased Options Remaining										108
Purchased options shares received								35
Common stock at an exercise price											$ 19.55	$ 19.31
Proceeds from issuance of warrants											391,000,000
Warrants exercised													109,000,000
Shares issues for exercised warrants														29
Conversion premium based on the closing price											53.00%
Closing price per share												$ 12.61
Aggregate notional amount of interest rate swap contracts designated as cash flow hedges																				900,000,000
Losses on swaps at time of settlement, deferred																			176,000,000
Losses reclassified from other comprehensive income and recognized as interest expense																		$ 6,000,000