Divestitures Divestitures - Other Assets and Liabilities Held for Sale (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Cash proceeds from divestitures, net			$ 413,479	$ 6,857
Gain on sale of business, before income taxes	$ 0	$ 0	218,705	0
Current assets	0		0		$ 39,152
Goodwill					14,400
Other intangibles, net of amortization					3,600
Current liabilities	$ 0		0		1,938
Assets held for sale, excluding discontinued operations
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Cash proceeds from divestitures, net			413,500
Gain on sale of business, before income taxes			$ 218,700
Current assets					39,152
Net, property, plant and equipment					121,759
Goodwill					14,422
Other intangibles, net of amortization					3,632
Assets held for sale					178,965
Current liabilities					1,938
Noncurrent liabilities					614
Liabilities held for sale					$ 2,552
Chemetall Surface Treatment
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Working capital settlement				$ 6,900