Other Income, Net - Additional Information (Detail) $ in Thousands		3 Months Ended							12 Months Ended
	May 30, 2018 USD ($)	Dec. 31, 2020 USD ($)	Mar. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)	Sep. 30, 2019 USD ($)	Jun. 30, 2019 USD ($)	Sep. 30, 2018 USD ($)	Mar. 31, 2018 USD ($) Parcel	Dec. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)
Disclosure Other Income Net Additional Information Detail [Line Items]
Dividends and interest income									$ 4,800	$ 10,900	$ 26,100
Gain on securities transaction recognized									(100)	300	12,400
Insurance recoveries						$ 7,700			1,600	7,700	1,300
Number of land parcels | Parcel								2
Net proceeds										4,600	19,500
Pre-tax gain on sale of land		$ 4,000						$ 11,900
Gain on sale of business				$ 3,000					$ 4,900	3,000	58,400
Kronos Worldwide, Inc.
Disclosure Other Income Net Additional Information Detail [Line Items]
Gain on insurance settlement related to property damage claim			$ 1,500	2,600
Tremont
Disclosure Other Income Net Additional Information Detail [Line Items]
Net proceeds								18,900
Tremont | Promissory Note
Disclosure Other Income Net Additional Information Detail [Line Items]
Principal payment of debt								$ 2,200
Amalgamated Sugar Company LLC
Disclosure Other Income Net Additional Information Detail [Line Items]
Dividends and interest income											16,900
Snake River
Disclosure Other Income Net Additional Information Detail [Line Items]
Gain on securities transaction recognized	$ 12,500						$ 12,500				12,500
NL
Disclosure Other Income Net Additional Information Detail [Line Items]
Insurance recoveries										$ 5,100
Net proceeds					$ 4,600						$ 600
Pre-tax gain on sale of land					$ 4,400
NL | Insurance and Risk Management Business
Disclosure Other Income Net Additional Information Detail [Line Items]
Proceeds from sale of business				3,250
Gain on sale of business				$ 3,000