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Goodwill - Additional Information (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Goodwill [Line Items]
Increase (decrease) in carrying amount of goodwill	$ 0.0	$ 0.0	$ 0.0
Goodwill impairment	0.0	$ 0.0	$ 0.0
Gross goodwill	$ 43.7
EWI Re, Inc.
Goodwill [Line Items]
Goodwill impairment				$ 6.4
CompX \| Marine Components
Goodwill [Line Items]
Goodwill impairment				$ 10.1