Business Combinations, Dispositions and Related Transactions - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended			12 Months Ended
	Dec. 31, 2020	Mar. 31, 2018	Jun. 30, 2017	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Waste Management
Business Combinations Discontinued Operations And Related Transactions [Line Items]
Pre-tax gain from disposal of discontinued operations	$ 4.9					$ 58.4
Impairment of long lived assets held for use			$ 170.6
Gain from disposal of discontinued operations, net of tax						$ 34.7
Waste Management | Discontinued Operations
Business Combinations Discontinued Operations And Related Transactions [Line Items]
Pre-tax gain from disposal of discontinued operations	4.9	$ 58.0
Gain from disposal of discontinued operations, net of tax	$ 4.3	$ 34.7
Gain on disposal of discontinued operations, per diluted share, net of tax	$ 0.15	$ 1.22
Kronos Worldwide, Inc.
Business Combinations Discontinued Operations And Related Transactions [Line Items]
Repurchase of common stock							2,000,000.0
Repurchased shares				122,489	264,992	0
Shares available for purchase	1,560,000			1,560,000
Stock repurchase, aggregate purchase price				$ 1.0	$ 3.0
CompX | Class A
Business Combinations Discontinued Operations And Related Transactions [Line Items]
Repurchased shares				0	0	0
Shares available for purchase	678,000			678,000