Financing Arrangements - Additional Information (Detail) (USD $)	1 Months Ended		3 Months Ended	6 Months Ended
	Sep. 30, 2012	Jun. 10, 2008	Oct. 26, 2012	Oct. 26, 2012 D	Apr. 27, 2012
Debt Disclosure [Line Items]
Conversion price of notes to shares of common stock			$ 31.85	$ 31.85
Note repurchase price, percentage of principal amount of notes				100.00%
Number of business days after measurement period				5
Convertible notes, measurement period for conversion, days				5
Trading price of convertible notes during measurement period, maximum percentage			98.00%
Trading price of convertible notes during measurement period, percentage			130.00%
Convertible notes, conversion threshold price	$ 41.41
Convertible notes, number of trading days during the 30 consecutive trading days ended June 30, 2012 during which common stock price did not exceed the conversion threshold price	20 days
Convertible notes, number of consecutive trading days during which Common stock price did not exceed the conversion threshold price	30 days
Closing price of common stock			$ 27.88	$ 27.88
Fair value of notes		1,017,000,000	1,340,200,000	1,340,200,000
Effective interest rate		6.31%
Debt discounts		248,000,000
Note hedges number of shares contracted to sell			31,800,000	31,800,000	31,800,000
Note hedge exercise price			$ 31.85	$ 31.85	$ 31.85
Unhedged portion of notes			20.00%	20.00%
Fair value percentage of face value of senior debt			106.00%	106.00%
Warrant
Debt Disclosure [Line Items]
Outstanding warrants, number of shares			39,700,000	39,700,000	39,700,000
Exercise price of warrants			41.28	41.28	41.28
Convertible Senior Notes 1.75%
Debt Disclosure [Line Items]
Senior notes		1,265,000,000	1,264,900,000	1,264,900,000	1,264,900,000
Senior notes, stated annual interest rate percentage		1.75%
Senior notes, maturity date				Jun. 01, 2013
Numerator of common stock ratio for convertible notes			31.40	31.40
Denominator of principal amount upon which conversion rate is based			1,000	1,000
Conversion price of notes to shares of common stock			$ 31.85	$ 31.85
Debt discounts			35,500,000	35,500,000	62,600,000
Equity Component
Debt Disclosure [Line Items]
Issuance costs on equity		5,200,000
Liability Component
Debt Disclosure [Line Items]
Issuance costs on equity		$ 21,400,000