Goodwill and other intangible assets - Changes in Carrying Amount of Goodwill (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended	12 Months Ended					12 Months Ended
Dec. 31, 2012	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2012 Chemicals [Member]	Dec. 31, 2011 Chemicals [Member]	Dec. 31, 2010 Chemicals [Member]	Dec. 31, 2009 Chemicals [Member]	Dec. 31, 2012 Component Products [Member]	Dec. 31, 2011 Component Products [Member]	Dec. 31, 2010 Component Products [Member]	Dec. 31, 2012 EWI [Member]	Dec. 31, 2010 EWI [Member]	Dec. 31, 2009 EWI [Member]
Goodwill [Line Items]
Beginning Balance		$ 400.1	$ 397.4	$ 396.9	$ 352.6	$ 352.6	$ 352.6	$ 352.6	$ 41.1	$ 38.4	$ 37.9	$ 6.4	$ 6.4	$ 6.4
Sale of discontinued operations		(14.3)							(14.3)
Goodwill impairment	5.3	6.4										6.4
Changes in foreign exchange rates		0.3	(0.4)	0.5					0.3	(0.4)	0.5
Goodwill acquired			3.1							3.1
Ending Balance	$ 379.7	$ 379.7	$ 400.1	$ 397.4	$ 352.6	$ 352.6	$ 352.6	$ 352.6	$ 27.1	$ 41.1	$ 38.4		$ 6.4	$ 6.4

Carrying amount as of the balance sheet date, which is the cumulative amount paid and (if applicable) the fair value of any noncontrolling interest in the acquiree, adjusted for any amortization recognized prior to the adoption of any changes in generally accepted accounting principles (as applicable) and for any impairment charges, in excess of the fair value of net assets acquired in one or more business combination transactions.

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+ Details

- Definition

The aggregate amount of goodwill acquired in the period and allocated to the reportable segment. The value is stated at fair value based on the purchase price allocation.

+ References+ Details

- Definition

Loss recognized during the period that results from the write-down of goodwill after comparing the implied fair value of reporting unit goodwill with the carrying amount of that goodwill. Goodwill is assessed at least annually for impairment.

+ References

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+ Details

- Definition

Write-off of the carrying amount of goodwill associated with all or a portion of a reporting unit that is sold in the period.

+ References+ Details