Other Income, Net - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended			9 Months Ended
	Sep. 30, 2020	Mar. 31, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Disclosure Other Income Net Additional Information Detail [Line Items]
Insurance recoveries			$ 0.2	$ 1.6	$ 5.2
Net proceeds					4.8
Infrastructure reimbursement				19.6	9.2
NL
Disclosure Other Income Net Additional Information Detail [Line Items]
Insurance recoveries					5.2
Net proceeds			4.6
Pre-tax gain on sale of land			$ 4.4
Kronos Worldwide, Inc.
Disclosure Other Income Net Additional Information Detail [Line Items]
Gain on insurance settlement related to property damage claim		$ 1.5
BMI
Disclosure Other Income Net Additional Information Detail [Line Items]
Pre-tax gain on sale of land	$ 4.0
City Of Henderson
Disclosure Other Income Net Additional Information Detail [Line Items]
Infrastructure reimbursement				$ 19.1	$ 8.8