Accounts Payable and Accrued Liabilities - Schedule of Accounts Payable and Accrued Liabilities (Detail) - USD ($) $ in Millions	Sep. 30, 2015	Dec. 31, 2014
Payable to affiliates:
Employee benefits	$ 29.3	$ 34.6
Deferred income	33.5	19.8
Environmental remediation and related costs	10.2	10.2
Accrued workforce reduction costs	15.2
Accrued sales discounts and rebates	20.9	23.0
Other	32.8	40.4
Total	283.3	310.2
Kronos Worldwide, Inc.
Accounts payable:
Accounts payable	88.0	121.4
CompX
Accounts payable:
Accounts payable	3.1	3.9
WCS
Accounts payable:
Accounts payable	1.3	1.4
BMI and LandWell
Accounts payable:
Accounts payable	2.0	7.0
NL
Accounts payable:
Accounts payable	2.0	2.3
Other
Accounts payable:
Accounts payable	0.3	0.2
Contran | Trade Accounts Payables
Payable to affiliates:
Payable to affiliates	26.1	26.1
LPC | Trade Accounts Payables
Payable to affiliates:
Payable to affiliates	15.1	$ 19.9
Interest Rate Swap Contract
Payable to affiliates:
Hedging liabilities	$ 3.5