Acquisitions (Details) - USD ($) $ in Thousands			3 Months Ended		6 Months Ended		12 Months Ended
	Feb. 01, 2017	Dec. 31, 2016	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016	Dec. 31, 2016
Business Acquisition [Line Items]
Inventories		$ 450,263	$ 565,894		$ 565,894		$ 450,263
Cash paid for inventory					39,525	$ 0
Gain on acquisition					7,433	0
Acquisition and integration related costs			0	$ 19,030	0	37,588
Jiangxi Jiangli New Materials Science and Technology Co. Ltd.
Business Acquisition [Line Items]
Total purchase price		145,000
Property, plant and equipment		29,000					29,000
Other intangibles		32,000					32,000
Deferred tax liabilities		3,700					3,700
Fair value of net working capital		$ 6,200					6,200
Inventories			37,000		37,000
Cash paid for inventory			11,800		31,200
Inventory markup			23,000		23,000
Acquired finite-lived intangible assets, weighted average useful life		17 years
Sales de Magnesio Ltda.
Business Acquisition [Line Items]
Total purchase price	$ 8,300
Percentage of equity interests acquired	50.00%
Gain on acquisition					7,400
Rockwood Holdings, Inc.
Business Acquisition [Line Items]
Acquisition and integration related costs				18,400		36,100
Other significant projects
Business Acquisition [Line Items]
Acquisition and integration related costs				$ 600		$ 1,500
Lithium and Advanced Materials | Jiangxi Jiangli New Materials Science and Technology Co. Ltd.
Business Acquisition [Line Items]
Goodwill							$ 87,700
Patents and technology | Jiangxi Jiangli New Materials Science and Technology Co. Ltd.
Business Acquisition [Line Items]
Acquired finite-lived intangible assets, weighted average useful life		20 years
Customer lists and relationships | Jiangxi Jiangli New Materials Science and Technology Co. Ltd.
Business Acquisition [Line Items]
Acquired finite-lived intangible assets, weighted average useful life		18 years
Other | Jiangxi Jiangli New Materials Science and Technology Co. Ltd.
Business Acquisition [Line Items]
Acquired finite-lived intangible assets, weighted average useful life		3 years
Cost of goods sold
Business Acquisition [Line Items]
Acquisition and integration related costs			1,800		10,700
Cost of goods sold | Jiangxi Jiangli New Materials Science and Technology Co. Ltd.
Business Acquisition [Line Items]
Utilization of inventory markup			11,900		22,500
Selling, general and administrative expenses
Business Acquisition [Line Items]
Acquisition and integration related costs			$ 4,700		$ 10,100