Financing Arrangements - Schedule of Notes (Detail) - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014	Sep. 30, 2014
Convertible Senior Notes [Line Items]
Net carrying amount	$ 419,426	$ 356,602
Convertible Debt
Convertible Senior Notes [Line Items]
Proceeds	250,000	250,000	$ 250,000
Less: debt discount, net of amortization	(31,824)	(37,148)
Net carrying amount	218,176	212,852
Equity component	$ 39,287	$ 39,287