Segment Information - Summarized Financial Information by Reportable Segments (Footnote) (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
	Sep. 30, 2017	Sep. 30, 2017	Sep. 30, 2016	Feb. 01, 2017
Segment Reporting Information [Line Items]
Loss on extinguishment of debt		$ 52,801	$ 0
Jiangxi Jiangli New Materials Science and Technology Co. Ltd.
Segment Reporting Information [Line Items]
Inventory markup	$ 23,100	23,100
Sales de Magnesio Ltda.
Segment Reporting Information [Line Items]
Percentage of equity interests acquired				50.00%
Cost of goods sold
Segment Reporting Information [Line Items]
Reversal of a liability from abandoned project	1,300	1,300
Restructuring and other, net		2,900
Cost of goods sold | Jiangxi Jiangli New Materials Science and Technology Co. Ltd.
Segment Reporting Information [Line Items]
Utilization of inventory markup	600	23,100
Selling, general and administrative expenses
Segment Reporting Information [Line Items]
Reversal of purchase accounting accrual		1,000
Restructuring and other, net		8,400
Research and development expenses
Segment Reporting Information [Line Items]
Fixed assets write-off			1,400
Restructuring and other, net		5,800
Other (expenses) income, net
Segment Reporting Information [Line Items]
Reversal of a liability from previous business	1,100	1,100
Revision of tax indemnification expense	$ 700	1,900
Asset retirement obligation charges		3,200
Net gain (loss) on sale of properties		(2,100)	$ 900
Final settlement claims on previous business disposal		$ 2,000