Interest Expense on Convertible Senior Notes (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012
Debt Instrument
Contractual interest expense on the coupon	$ 8,550	$ 8,550
Amortization of the discount component and debt issue fees recognized as interest expense	16,628	14,612
Total interest expense on the convertible debt	$ 25,178	$ 23,162