Summary of significant accounting policies - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Basis Of Presentation And Significant Accounting Policies [Line Items]
Capitalized interest cost on property and equipment	$ 1.7	$ 3.3	$ 0.9
Earnings of foreign subsidiaries subject to permanent reinvestment plan	1,000.0	978.0
Percentage of likelihood for recognition of uncertain tax positions	50.00%
Shipping and handling costs	89	93	83
Advertising costs	1	2	1
Research, development and certain sales technical support costs	19	20	13
Minimum [Member]
Basis Of Presentation And Significant Accounting Policies [Line Items]
Percentage of investment required to report under equity method investment	20.00%
Contran [Member]
Basis Of Presentation And Significant Accounting Policies [Line Items]
Controlling interest in subsidiary	93.00%
Net cash payment for income tax	6.0	10.3	16.1
Capitalized Operating Permit Costs [Member] | WCS [Member]
Basis Of Presentation And Significant Accounting Policies [Line Items]
Amortization of capitalized operating permit costs	4.9	1.3	1.3
Amortization of capitalized operating permit, 2013	6.7
Amortization of capitalized operating permit, 2014	6.7
Amortization of capitalized operating permit, 2015	6.7
Amortization of capitalized operating permit, 2016	6.7
Amortization of capitalized operating permit, 2017	$ 6.7