Components of Non-Cash Convertible Debt Related Expense (Detail) (USD $) In Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2011	Jun. 30, 2010	Jun. 30, 2011	Jun. 30, 2010
Debt Conversion [Line Items]
Total non-cash convertible debt related expense	$ 6,425	$ 11,734	$ 11,585	$ 19,981
3.25% Cash Convertible Senior Notes due 2014
Debt Conversion [Line Items]
Debt discount accretion	5,805	5,247	11,465	10,363
3.25% Cash Convertible Senior Notes due 2014 | Convertible Note Hedge
Debt Conversion [Line Items]
Fair value changes related to the derivative	14,620	7,045	23,857	43,941
3.25% Cash Convertible Senior Notes due 2014 | Cash Conversion Option
Debt Conversion [Line Items]
Fair value changes related to the derivative	(14,758)	(5,704)	(25,270)	(44,523)
1.00% Senior Convertible Debentures due 2027
Debt Conversion [Line Items]
Debt discount accretion	$ 758	$ 5,146	$ 1,533	$ 10,200