Convertible Notes Convertible Notes (Interest Expense for February 2018 Notes) (Detail) (Details) - February 2018 Notes [Member] - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Debt Instrument [Line Items]
Contractual coupon interest	$ 2,464	$ 3,000	$ 4,928	$ 6,000
Amortization of debt issuance costs	442	546	880	1,089
Amortization of debt discount	1,555	1,776	3,105	3,523
Total	$ 4,461	$ 5,322	$ 8,913	$ 10,612