Business and geographic segments - Total Assets Held by Business Segments (Detail) (USD $) In Millions, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Segment Reporting Information [Line Items]
Total assets	$ 3,170.5	$ 2,838.0	$ 2,714.3
Chemicals [Member]
Segment Reporting Information [Line Items]
Total assets	2,401.1	2,189.7	2,101.4
Component Products [Member]
Segment Reporting Information [Line Items]
Total assets	82.3	141.4	141.5
Waste Management [Member]
Segment Reporting Information [Line Items]
Total assets	265.0	223.4	166.4
Ti02manufacturing Joint Venture [Member]
Segment Reporting Information [Line Items]
Total assets	16.2	16.5	17.0
Corporate and eliminations [Member]
Segment Reporting Information [Line Items]
Total assets	$ 405.9	$ 267.0	$ 288.0