Segment and Geographic Area Information Summarized Financial Information by Reportable Segments (Footnote) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Feb. 01, 2017
Segment Reporting Information [Line Items]
Multiemployer plan, period contributions	$ 1,500	$ 1,500	$ 1,700
Loss on extinguishment of debt	0	(52,801)	(1,921)
Cost of sales
Segment Reporting Information [Line Items]
Restructuring and other, net	100	2,900
Write-off of fixed assets	4,900
Non-routine Chilean labor costs	8,800
Reversal of a liability from an abandoned project		1,300
Research and development expenses
Segment Reporting Information [Line Items]
Restructuring and other, net		5,700
Write-off of fixed assets			1,400
Selling, general and administrative expenses
Segment Reporting Information [Line Items]
Restructuring and other, net	3,700	8,400
Charitable contribution	1,200
Gain related to a refund form Chilean authorities	1,500
Reversal of purchase accounting accrual		1,000
Net gain (loss) on sales of properties			(900)
Other expenses, net
Segment Reporting Information [Line Items]
Revision of tax indemnification expense	19,700	3,700
Revision of previously recorded expenses of a disposed business	5,500
Reversal of a liability from previous business	1,500	1,100
Asset retirement obligation charges		3,200
Net gain (loss) on sales of properties		(8,700)	1,100
Settlement of a legal claim		1,000
Reversal of a liability from previous acquisition		10,600
Environmental charges			$ 2,400
Jiangxi Jiangli New Materials Science and Technology Co. Ltd.
Segment Reporting Information [Line Items]
Inventory markup		23,100
Sales de Magnesio Ltda.
Segment Reporting Information [Line Items]
Percentage of equity interests acquired				50.00%
Financial Improvement Plan | Selling, general and administrative expenses
Segment Reporting Information [Line Items]
Multiemployer plan, period contributions	$ 2,300	$ 3,300