Investment in Kronos Worldwide, Inc. - Additional Information (Detail) - Kronos - USD ($) $ / shares in Units, shares in Millions, $ in Millions |
Dec. 31, 2015 |
Dec. 31, 2014 |
|---|---|---|
| Schedule Of Equity Method Investments [Line Items] | ||
| Outstanding common stock, shares | 35.2 | 35.2 |
| Aggregate market value | $ 198.6 | $ 458.6 |
| Common stock quoted market price per share | $ 5.64 | $ 13.02 |