Goodwill and other intangible assets, net - Intangible Assets (Details) - USD ($) $ in Millions	Jun. 30, 2017	Dec. 31, 2016
Finite-Lived Intangible Assets, Net
Net	$ 6.1	$ 7.3
Performance Chemicals
Finite-Lived Intangible Assets, Net
Gross carrying amount	42.1	42.1
Accumulated amortization	36.0	34.8
Net	6.1	7.3
Performance Chemicals \| Brands
Finite-Lived Intangible Assets, Net
Gross carrying amount	13.9	13.9
Accumulated amortization	11.6	11.3
Net	2.3	2.6
Performance Chemicals \| Customer contracts and relationships
Finite-Lived Intangible Assets, Net
Gross carrying amount	28.2	28.2
Accumulated amortization	24.4	23.5
Net	$ 3.8	$ 4.7

Accumulated amount of amortization of assets, excluding financial assets and goodwill, lacking physical substance with a finite life.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 30
-Section 50
-Paragraph 2
-Subparagraph (a)(1)
-URI http://asc.fasb.org/extlink&oid=66006027&loc=d3e16323-109275

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Amount before amortization of assets, excluding financial assets and goodwill, lacking physical substance with a finite life.

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Amount after amortization of assets, excluding financial assets and goodwill, lacking physical substance with a finite life.

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