Discontinued operations - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended		3 Months Ended		1 Months Ended
Mar. 31, 2013	Mar. 31, 2013 CompX [Member]	Mar. 31, 2013 CompX [Member] Taiwan Land [Member]	Dec. 31, 2012 CompX [Member] Taiwan Land [Member]	Apr. 30, 2013 CompX [Member] Taiwan Land [Member] Scenario, Forecast [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Promissory note receivable				$ 3.0
Promissory note receivable		1.6	3.0
Cash collected on notes receivable	$ 1.8		$ 1.8		$ 1.2

An amount representing an agreement for an unconditional promise by the maker to pay the Company (holder) a definite sum of money within one year from the balance sheet date (or the normal operating cycle, whichever is longer), net of any write-downs taken for collection uncertainty on the part of the holder. Such amount may include accrued interest receivable in accordance with the terms of the debt. The debt also may contain provisions and related items including a discount or premium, payable on demand, secured, or unsecured, interest bearing or noninterest bearing, among a myriad of other features and characteristics. This amount does not include amounts related to receivables held-for-sale.

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The cash inflow associated with principal collections from a borrowing supported by a written promise to pay an obligation.

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