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, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Debt Instrument [Line Items]
Contractual coupon interest	$ 1,264	$ 2,464	$ 2,529	$ 4,928
Amortization of debt issuance costs	250	442	499	880
Amortization of debt discount	851	1,555	1,699	3,105
Total	$ 2,365	$ 4,461	$ 4,727	$ 8,913