Business and geographic segments - Holding Percentage of Subsidiaries (Detail)	Dec. 31, 2012
Kronos Worldwide, Inc. [Member]
Segment Reporting Information [Line Items]
Controlling interest in business segments	80.00%
CompX [Member]
Segment Reporting Information [Line Items]
Controlling interest in business segments	87.00%
WCS [Member]
Segment Reporting Information [Line Items]
Controlling interest in business segments	100.00%

The parent entity's interest in net assets of the subsidiary, expressed as a percentage.

No definition available.

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