Convertible Notes (Interest Expense for the Series 2012 Notes) (Detail) (Series 2012 Notes [Member], USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Series 2012 Notes [Member]
Debt Instrument [Line Items]
Contractual coupon interest	$ 1,287	$ 1,287	$ 2,573	$ 2,550
Amortization of debt issuance costs	287	277	571	548
Amortization of debt discount	1,513	1,415	3,000	2,780
Total	$ 3,087	$ 2,979	$ 6,144	$ 5,878