Stockholder's Equity - Additional Information (Detail) - USD ($)	3 Months Ended	12 Months Ended
	Mar. 31, 2014	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Class Of Stock [Line Items]
Dividends paid	$ 0
NL
Class Of Stock [Line Items]
Common stock awarded to board of directors		14,000	9,000	9,000
Shares available for award		163,000
NL | Maximum
Class Of Stock [Line Items]
Aggregate of common stock awarded to directors		200,000
CompX
Class Of Stock [Line Items]
Shares available for award		173,000
CompX | Maximum
Class Of Stock [Line Items]
Aggregate of common stock awarded to directors		200,000
Kronos
Class Of Stock [Line Items]
Shares available for award		163,500
Kronos | Maximum
Class Of Stock [Line Items]
Aggregate of common stock awarded to directors		200,000