Long Term Debt - Additional Information (Detail) (USD $)	1 Months Ended		3 Months Ended			1 Months Ended	3 Months Ended			1 Months Ended	3 Months Ended		3 Months Ended
	May 31, 2011	May 31, 2011 0.50% Convertible Senior Notes Due 2016	Sep. 23, 2012 0.50% Convertible Senior Notes Due 2016 D	Jun. 24, 2012 0.50% Convertible Senior Notes Due 2016	Sep. 23, 2012 0.50% Convertible Senior Notes Due 2016 Convertible Note Hedge	May 31, 2011 1.25% Convertible Senior Notes Due 2018	Sep. 23, 2012 1.25% Convertible Senior Notes Due 2018 D	Jun. 24, 2012 1.25% Convertible Senior Notes Due 2018	Sep. 23, 2012 1.25% Convertible Senior Notes Due 2018 Convertible Note Hedge	Jun. 24, 2012 2.625% Convertible Senior Notes maturing in 2041 Note	Sep. 23, 2012 2.625% Convertible Senior Notes maturing in 2041 D	Jun. 04, 2012 2.625% Convertible Senior Notes maturing in 2041	Sep. 23, 2012 2.625% Convertible Senior Notes maturing in 2041 On or after May 21, 2021, we may redeem all or part of the 2041 Notes for the principal plus any accrued and unpaid interest D
Debt Instrument [Line Items]
Aggregate principal amount of notes		$ 450,000,000	$ 450,000,000	$ 450,000,000		$ 450,000,000	$ 450,000,000	$ 450,000,000		$ 699,900,000	$ 699,900,000
Annual interest rate paid by cash semi-annually		0.50%	0.50%	0.50%		1.25%	1.25%	1.25%		2.625%	2.625%
Initial conversion rate of common stock shares		15.8687				15.8687				28.4781
Convertible Senior Notes conversion price		$ 63.02	$ 63.02			$ 63.02	$ 63.02			$ 35.11
Principal amount of convertible debt conversion increments		1,000				1,000				1,000	1,000
Net proceeds from the sale of Convertible Senior Notes	835,500,000
Debt instruments maturity date			2016				2018				2041
Initial carrying value of liability component of convertible notes		373,800,000				345,100,000						509,500,000
Discount rate used to determine liability fair value		4.29%	4.29%			5.27%	5.27%				4.28%
Carrying value of equity components			76,200,000				104,900,000				328,100,000
Unamortized discount balance			56,700,000	60,300,000			87,100,000	90,400,000		190,300,000	189,500,000
Remaining life of bond discount, years			3 years 7 months 6 days				5 years 7 months 6 days				28 years 7 months 6 days
Percentage of product last reported sale price of common stock			98.00%				98.00%				98.00%
Number of days on which common stock sale price was greater than or equal to 130% of conversion price, in a period of 30 consecutive trading days ending on the last trading day of the immediately preceding fiscal quarter			20				20				20		20
Number of consecutive trading days period required			30				30				30		30
Stock price percentage of conversion price			130.00%				130.00%				130.00%		150.00%
Percentage of principal amounts being repurchased			100.00%				100.00%				100.00%
Warrant conversion price			71.34		71.34		76.10		76.10
Shares of common stock agreed to sell			7,100,000				7,100,000
Cost of convertible bond hedge			76,200,000				104,900,000
Convertible bond hedge at inception of the transaction on stockholders' equity			28,200,000				38,800,000
Proceeds from sale of warrants			57,600,000				76,300,000
Shares issued under warrants			7,100,000				7,100,000
Number of Debt converted to shares of common stock										65
Debt converted, par value										65,000
Debt converted, number of common shares issued										137
Maximum amount of contingent interest rate											2.10%
Fair value of notes			$ 431,100,000				$ 440,100,000				$ 792,100,000