Convertible Debt - Key Components of Convertible Debt (Detail) (Convertible Senior Notes 2011 and 2013, USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Convertible Senior Notes 2011 and 2013
Debt Instrument [Line Items]
Contractual interest expense on the coupon	$ 29,908	$ 57,646	$ 60,375
Amortization of the discount component recognized as interest expense	60,633	115,904	114,481
Total interest expense on the convertible debt	$ 90,541	$ 173,550	$ 174,856