Key Components of Convertible Debt (Detail) (USD $)	3 Months Ended
	Mar. 31, 2012	Mar. 31, 2011
Debt Instrument [Line Items]
Contractual interest expense on the coupon	$ 7,523,000	$ 15,094,000
Amortization of the discount component recognized as interest expense	14,700,000	29,363,000
Total interest expense on the convertible debt	$ 22,223,000	$ 44,457,000