Other noncurrent assets - Investment in Affiliates and Other Assets (Detail) (USD $) In Millions, unless otherwise specified	Sep. 30, 2012	Dec. 31, 2011
Other Noncurrent Assets [Line Items]
Investment in affiliates	$ 135.8	$ 105.7
Other noncurrent assets:
Waste disposal site operating permits, net	67.0	66.6
Restricted cash	11.5	7.6
Deferred financing costs	7.3	2.0
Assets held for sale	6.9	7.3
IBNR receivables	6.9	6.5
Capital lease deposit	6.2	6.2
Other intangible assets	1.6	2.1
Other	43.8	67.9
Total	151.2	166.2
TiO2 Manufacturing Joint Venture, Louisiana Pigment Company, L.P. ("LPC") [Member]
Other Noncurrent Assets [Line Items]
Investment in affiliates	119.3	89.2
Other [Member]
Other Noncurrent Assets [Line Items]
Investment in affiliates	$ 16.5	$ 16.5