Financing Arrangements - Summary of Carrying Amounts of Debt (Detail) - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014
Debt Instrument [Line Items]
Net carrying amount	$ 419,426	$ 356,602
Current maturities of debt	0	(28,750)
Long-term debt, net of current portion	419,426	327,852
1.25% convertible senior notes due 2019
Debt Instrument [Line Items]
Net carrying amount	218,176	212,852
Senior secured credit facility
Debt Instrument [Line Items]
Net carrying amount	$ 201,250	$ 143,750