Goodwill and other intangible assets, net - Intangible Assets (Details) - USD ($) $ in Millions	Jun. 30, 2016	Dec. 31, 2015
Finite-Lived Intangible Assets, Net
Net	$ 8.7	$ 10.0
Performance Chemicals
Finite-Lived Intangible Assets, Net
Gross carrying amount	42.7	42.5
Accumulated amortization	34.0	32.5
Net	8.7	10.0
Brands \| Performance Chemicals
Finite-Lived Intangible Assets, Net
Gross carrying amount	13.9	13.7
Accumulated amortization	11.0	10.6
Net	2.9	3.1
Customer contracts and relationships \| Performance Chemicals
Finite-Lived Intangible Assets, Net
Gross carrying amount	28.2	28.2
Accumulated amortization	22.5	21.4
Net	5.7	6.8
Other \| Performance Chemicals
Finite-Lived Intangible Assets, Net
Gross carrying amount	0.6	0.6
Accumulated amortization	0.5	0.5
Net	$ 0.1	$ 0.1

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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