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Marketable Securities - Schedule of Marketable Securities (Detail) (Level 1 [Member], Valhi common stock [Member], USD $)
In Thousands, unless otherwise specified
Mar. 31, 2013
Dec. 31, 2012
Level 1 [Member] | Valhi common stock [Member]
   
Schedule of Available-for-sale Securities [Line Items]    
Market value $ 230,686 $ 179,662
Cost basis 24,347 24,347
Unrealized gains (losses) $ 206,339 $ 155,315