Financing Arrangements and Fair Value of Financial Instruments (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Debt Instrument [Line Items]
Long-term debt, gross	$ 207,418	$ 183,118
Unamortized discount and debt issuance costs	(19,020)	(22,643)
Long-term debt	188,398	160,475
Long-term debt, current maturities, gross	(6,453)	(1,518)
Unamortized discount and debt issuance costs, current	0	0
Long-term debt, current maturities	(6,453)	(1,518)
Long-term debt, excluding current maturities, gross	200,965	181,600
Unamortized discount and debt issuance costs, noncurrent	(19,020)	(22,643)
Long-term debt, excluding current maturities	181,945	158,957
Other Debt
Debt Instrument [Line Items]
Long-term debt, gross	7,218	1,518
Long-term debt	7,218	1,518
Senior notes | Convertible Notes due 2021
Debt Instrument [Line Items]
Long-term debt, gross	100,000	100,000
Unamortized discount and debt issuance costs	(19,020)	(22,643)
Long-term debt	80,980	77,357
Revolving credit facility | ABL Facility
Debt Instrument [Line Items]
Long-term debt, gross	100,200	81,600
Long-term debt	$ 100,200	$ 81,600