Commitments and contingencies - Approximate Percentage of TiO2 Sales by Volume for Segments (Detail) (Geographic Concentration Risk [Member], Component Segment [Member])	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Europe [Member]
Schedule Of Sales Revenue By Business Segment [Line Items]
Sale of TiO2, percentage	47.00%	53.00%	53.00%
North America [Member]
Schedule Of Sales Revenue By Business Segment [Line Items]
Sale of TiO2, percentage	35.00%	32.00%	33.00%

The percentage of net product revenue to total net revenue from the sale of goods as of year end.

No definition available.

Name:	us-gaap_SalesRevenueGoodsNetPercentage
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant