Accounts and Other Receivables, Net - Components of Accounts and Other Receivables (Detail) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Trade accounts receivable:
VAT and other receivables	$ 27.2	$ 31.2
Allowance for doubtful accounts	(1.9)	(1.2)
Total	332.1	314.0
Trade Accounts Receivable | Kronos Worldwide, Inc.
Trade accounts receivable:
Accounts receivable	294.8	270.5
Trade Accounts Receivable | CompX
Trade accounts receivable:
Accounts receivable	10.8	11.9
Trade Accounts Receivable | BMI and LandWell
Trade accounts receivable:
Accounts receivable	$ 1.2	$ 1.6