Convertible Senior Notes Due 2017 - Interest Expense on Convertible Notes (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
Debt Disclosure [Abstract]
Coupon interest expense	$ 1,698	$ 1,698
Non-cash amortization of debt discount	3,257	2,943
Non-cash amortization of debt issuance costs	275	247
Total	$ 5,230	$ 4,888