Debt, net - Schedule of Debt (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Dec. 31, 2017	Oct. 05, 2017
Debt Instrument [Line Items]
Debt, net	$ 109,825	$ 108,429
3.75% convertible senior notes due 2020, net of discount
Debt Instrument [Line Items]
Debt, net	$ 109,327	$ 108,139
Debt instrument, maturity date	Mar. 01, 2020
Interest rate percentage	3.75%	3.75%	3.75%
Other indebtedness — 5.50% interest rate
Debt Instrument [Line Items]
Debt, net	$ 498	$ 290
Interest rate percentage	5.50%	5.50%