Acquisitions - Summary of Goodwill (Details) $ in Millions	6 Months Ended
Jun. 30, 2018 USD ($)
Goodwill [Roll Forward]
Balance, December 31, 2017	$ 402.4
Goodwill acquired during the year	139.7
Foreign currency translation	(0.9)
Balance, June 30, 2018	541.2
Catalysts Technologies
Goodwill [Roll Forward]
Balance, December 31, 2017	357.7
Goodwill acquired during the year	139.7
Foreign currency translation	(0.7)
Balance, June 30, 2018	496.7
Materials Technologies
Goodwill [Roll Forward]
Balance, December 31, 2017	44.7
Goodwill acquired during the year	0.0
Foreign currency translation	(0.2)
Balance, June 30, 2018	$ 44.5

Amount after accumulated impairment loss of an asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=35741047&loc=d3e13816-109267

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 20
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=6388280&loc=d3e13770-109266

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 20
-Section 45
-Paragraph 5
-URI http://asc.fasb.org/extlink&oid=77989000&loc=SL49117168-202975

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Amount of increase in asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized resulting from a business combination.

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Amount of foreign currency translation gain (loss) which increases (decreases) an asset representing future economic benefits from other assets acquired in a business combination that are not individually identified and separately recognized.

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