Restructuring, Impairment and Other Costs - Restructuring, Severance and Related Charges (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2018	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Restructuring Reserve [Roll Forward]
Accrued balance, beginning	$ 770	$ 770	$ 1,404	$ 773
Costs incurred	(600)	639	0	(5,264)
Payments		(131)	(634)	(2,627)
Expenses/charges		0	0	(2,006)
Accrued balance, ending		0	770	1,404
Employee Severance
Restructuring Reserve [Roll Forward]
Accrued balance, beginning	0	0	81	753
Costs incurred			0	(768)
Payments			(81)	(1,437)
Expenses/charges			0	(3)
Accrued balance, ending			0	81
Facility Closing
Restructuring Reserve [Roll Forward]
Accrued balance, beginning	770	770	1,323	20
Costs incurred		639	0	(2,779)
Payments		(131)	(553)	(1,190)
Expenses/charges		0	0	(286)
Accrued balance, ending		0	770	1,323
Spartanburg impairment
Restructuring Reserve [Roll Forward]
Accrued balance, beginning			0	0
Costs incurred				(546)
Payments				0
Expenses/charges				(546)
Accrued balance, ending				0
Fuel tank write-off
Restructuring Reserve [Roll Forward]
Accrued balance, beginning			0	0
Costs incurred				(524)
Payments				0
Expenses/charges				(524)
Accrued balance, ending				0
Executive Severance
Restructuring Reserve [Roll Forward]
Accrued balance, beginning	$ 35	35	277
Costs incurred		(711)	(930)	0
Payments		(499)	(1,172)
Expenses/charges		0	0
Accrued balance, ending		$ 247	35	277
Restatement Adjustment
Restructuring Reserve [Roll Forward]
Accrued balance, beginning			$ 0	0
Costs incurred				(647)
Payments				0
Expenses/charges				(647)
Accrued balance, ending				$ 0