Convertible Notes (Interest Expense for the May 2015 Notes) (Detail) (May 2015 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
May 2015 Notes [Member]
Debt Instrument [Line Items]
Contractual coupon interest	$ 1,455	$ 1,455	$ 2,911	$ 2,911
Amortization of debt issuance costs	307	297	611	592
Amortization of debt discount	1,194	1,110	2,366	2,200
Total	$ 2,956	$ 2,862	$ 5,888	$ 5,703