Convertible Notes (Interest Expense for the Series 2012 Notes) (Detail) - Series 2012 Notes [Member] - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Debt Instrument [Line Items]
Contractual coupon interest	$ 0	$ 347	$ 80	$ 1,455
Amortization of debt issuance costs	0	64	13	996
Amortization of debt discount	0	404	76	1,783
Total	$ 0	$ 815	$ 169	$ 4,234