Accounts and Other Receivables, Net - Components of Accounts and Other Receivables (Detail) - USD ($) $ in Millions	Sep. 30, 2021	Dec. 31, 2020
Trade accounts receivable:
VAT and other receivables	$ 26.7	$ 27.2
Refundable income taxes	7.8	5.7
Allowance for doubtful accounts	(2.1)	(1.9)
Total	412.4	342.3
Trade Accounts Receivable | Kronos Worldwide, Inc.
Trade accounts receivable:
Accounts receivable	346.6	294.8
Trade Accounts Receivable | CompX
Trade accounts receivable:
Accounts receivable	15.2	10.8
Trade Accounts Receivable | BMI and LandWell
Trade accounts receivable:
Accounts receivable	2.1	1.2
Contran | Trade Items
Trade accounts receivable:
Receivable from affiliates	0.4	1.7
Louisiana Pigment Company, L.P. ("LPC")
Trade accounts receivable:
Receivable from affiliates	13.4
Other | Trade Items
Trade accounts receivable:
Receivable from affiliates	$ 2.3	$ 2.8