Accounts Payable and Accrued Liabilities - Schedule of Accounts Payable and Accrued Liabilities (Detail) - USD ($) $ in Millions	Sep. 30, 2020	Dec. 31, 2019
Payable to affiliates:
Accrued litigation settlement	$ 11.8	$ 11.8
Employee benefits	38.2	30.6
Operating lease liabilities	6.7	6.2
Accrued sales discounts and rebates	25.5	33.7
Deferred income	28.2	10.3
Environmental remediation and related costs	4.3	4.5
Interest	1.5	5.2
Other	35.3	40.0
Total	281.1	307.4
Kronos Worldwide, Inc.
Accounts payable:
Accounts payable	108.9	137.2
CompX
Accounts payable:
Accounts payable	2.7	2.5
BMI and LandWell
Accounts payable:
Accounts payable	6.3	3.7
NL
Accounts payable:
Accounts payable		0.9
Other
Accounts payable:
Accounts payable	0.4	0.4
Contran | Income Taxes Payable
Payable to affiliates:
Payable to affiliates	5.7	4.0
LPC
Payable to affiliates:
Payable to affiliates	$ 5.6	$ 16.4