Key Components of Convertible Debt (Detail) (Convertible Senior Notes 2011 and 2013, USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Convertible Senior Notes 2011 and 2013
Debt Instrument [Line Items]
Contractual interest expense on the coupon	$ 7,482	$ 15,078	$ 22,427	$ 45,266
Amortization of the discount component recognized as interest expense	15,405	30,852	45,059	90,174
Total interest expense on the convertible debt	$ 22,887	$ 45,930	$ 67,486	$ 135,440