Accounts Payable and Accrued Liabilities - Components of Accounts Payable and Accrued Liabilities (Detail) - USD ($) $ in Millions	Sep. 30, 2018	Dec. 31, 2017
Accounts Payable And Accrued Liabilities [Line Items]
Accounts payable	$ 105.8	$ 107.9
Employee benefits	29.1	27.0
Accrued sales discounts and rebates	25.4	11.7
Other	33.8	43.0
Total	212.3	205.8
LPC
Accounts Payable And Accrued Liabilities [Line Items]
Payable to affiliate	12.7	$ 16.2
Valhi | Income taxes, net
Accounts Payable And Accrued Liabilities [Line Items]
Payable to affiliate	$ 5.5