Acquisitions (Details) - USD ($) $ in Thousands			3 Months Ended		12 Months Ended
	Feb. 01, 2017	Dec. 31, 2016	Mar. 31, 2017	Mar. 31, 2016	Dec. 31, 2016
Business Acquisition [Line Items]
Inventories		$ 450,263	$ 518,936		$ 450,263
Cash paid for inventory			27,742	$ 0
Gain on acquisition			7,433	0
Acquisition and integration related costs			0	18,558
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 assets		3,900			3,900
Fair value of net working capital		$ 6,200			6,200
Inventories			37,000
Cash paid for inventory			19,400
Inventory markup			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				16,900
Other significant projects
Business Acquisition [Line Items]
Acquisition and integration related costs				$ 1,700
Lithium and Advanced Materials | Jiangxi Jiangli New Materials Science and Technology Co. Ltd.
Business Acquisition [Line Items]
Goodwill					$ 87,900
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			8,900
Cost of goods sold | Jiangxi Jiangli New Materials Science and Technology Co. Ltd.
Business Acquisition [Line Items]
Utilization of inventory markup			10,600
Selling, general and administrative expenses
Business Acquisition [Line Items]
Acquisition and integration related costs			$ 5,400