Key Components of Convertible Debt (Detail) (Convertible Senior Notes 2011 and 2013, USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011
Convertible Senior Notes 2011 and 2013
Debt Instrument [Line Items]
Contractual interest expense on the coupon	$ 7,422	$ 15,094	$ 14,945	$ 30,188
Amortization of the discount component recognized as interest expense	14,954	29,959	29,654	59,322
Total interest expense on the convertible debt	$ 22,376	$ 45,053	$ 44,599	$ 89,510