Financing Arrangements and Fair Value of Financial Instruments (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Debt Instrument [Line Items]
Long-term debt, gross	$ 208,491	$ 183,118
Unamortized discount and debt issuance costs	(21,465)	(22,643)
Long-term debt	187,026	160,475
Long-term debt, current maturities, gross	(1,391)	(1,518)
Unamortized discount and debt issuance costs, current	0	0
Long-term debt, current maturities	(1,391)	(1,518)
Long-term debt, excluding current maturities, gross	207,100	181,600
Unamortized discount and debt issuance costs, noncurrent	(21,465)	(22,643)
Long-term debt, excluding current maturities	185,635	158,957
Other Debt
Debt Instrument [Line Items]
Long-term debt, gross	1,391	1,518
Long-term debt	1,391	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	(21,465)	(22,643)
Long-term debt	78,535	77,357
Revolving credit facility | ABL Facility
Debt Instrument [Line Items]
Long-term debt, gross	107,100	81,600
Long-term debt	$ 107,100	$ 81,600