Marketable Securities - Additional Information (Detail) - USD ($) $ / shares in Units, shares in Millions, $ in Millions |
3 Months Ended | 9 Months Ended | 12 Months Ended | ||
|---|---|---|---|---|---|
Feb. 29, 2016 |
Sep. 30, 2015 |
Sep. 30, 2015 |
Dec. 31, 2015 |
Dec. 31, 2014 |
|
| Schedule Of Available For Sale Securities [Line Items] | |||||
| Pre-tax impairment charge to write down | $ 12.0 | ||||
| Valhi Inc | |||||
| Schedule Of Available For Sale Securities [Line Items] | |||||
| Pre-tax impairment charge to write down | $ 12.0 | ||||
| Impairment charge realized loss, reclassified out of accumulated other comprehensive income along with related deferred income tax | $ 4.2 | ||||
| Valhi Inc | Common stock | |||||
| Schedule Of Available For Sale Securities [Line Items] | |||||
| Investments in publicly-traded shares | 1.7 | 1.7 | |||
| Quoted market price of per share | $ 1.34 | $ 6.41 | |||
| Valhi Inc | Common stock | Subsequent Event | |||||
| Schedule Of Available For Sale Securities [Line Items] | |||||
| Difference between aggregate quoted market price and aggregate cost | $ 1.0 |