Discontinued operations - Schedule of Condensed Income Statement (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2012
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Total discontinued operations, net of tax and noncontrolling interest	$ 0.7
Compx Furniture Components [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Net sales	15.1
Operating income	1.3
Income before taxes	1.3
Income tax expense	0.6
Income from discontinued operations, net of tax	0.7
Noncontrolling interest in income from discontinued operations	0.2
Compx Furniture Components [Member] | Net of Noncontrolling Interest [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Total discontinued operations, net of tax and noncontrolling interest	$ 0.5