Marketable Securities - Schedule of Marketable Securities (Detail) - USD ($) $ in Thousands |
Dec. 31, 2016 |
Dec. 31, 2015 |
|---|---|---|
| Schedule Of Available For Sale Securities [Line Items] | ||
| Market value | $ 49,731 | $ 19,260 |
| Level 1 | ||
| Schedule Of Available For Sale Securities [Line Items] | ||
| Market value | 49,731 | 19,260 |
| Level 1 | Valhi Inc | Common stock | ||
| Schedule Of Available For Sale Securities [Line Items] | ||
| Market value | 49,731 | 19,260 |
| Cost basis | 24,347 | 24,347 |
| Unrealized loss | $ (5,087) | |
| Unrealized gain | $ 25,384 |