Commitments and Contingencies - Lead Pigment Litigation and Environmental Matters and Litigation - Additional Information (Detail)		3 Months Ended			6 Months Ended	12 Months Ended
	Jul. 24, 2019 USD ($) Defendant Installment	Sep. 30, 2019 USD ($)	Jun. 30, 2019 USD ($)	Jun. 30, 2018 USD ($) Installment	Dec. 31, 2019 USD ($)	Dec. 31, 2020 USD ($) Cases site	Sep. 30, 2020 USD ($)	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)
Commitments And Contingent Liabilities [Line Items]
Litigation settlement					$ 11,800,000	$ 11,800,000		$ 11,800,000
Litigation settlement net present value					60,100,000	49,400,000		60,100,000
Litigation settlement expense, net			$ 19,300,000					19,300,000	$ 62,000,000.0
Current insurance recovery receivable					0	0		0
Accrual for reasonably estimable environmental remediation and related matters					99,700,000	98,600,000		99,700,000	$ 103,400,000	$ 117,500,000
Other Environmental Cleanup Matters
Commitments And Contingent Liabilities [Line Items]
Accrual for reasonably estimable environmental remediation and related matters						6,000,000
NL | Environmental Remediation Sites NL Named As PRP Or Defendant
Commitments And Contingent Liabilities [Line Items]
Accrual for reasonably estimable environmental remediation and related matters						$ 93,000,000
Number of sites associated with remediation and related costs | site						32
NL | Maximum | Environmental Remediation Sites NL Named As PRP Or Defendant
Commitments And Contingent Liabilities [Line Items]
Upper end range, estimate costs for remediation and related matters						$ 114,000,000
Lead Pigment Litigation | NL
Commitments And Contingent Liabilities [Line Items]
Number of cases settled and dismissed and found not liable | Cases						100
Period by which loss contingency claims settled and dismissed						30 years
California Lead Paint Litigation | NL
Commitments And Contingent Liabilities [Line Items]
Description of defendants						July 24, 2019, an order approving a global settlement agreement entered into among all of the plaintiffs and the three defendants remaining in the case (the Sherwin Williams Company, ConAgra Grocery Products and NL) was entered by the court and the case was dismissed with prejudice.  The global settlement agreement provides that an aggregate $305 million will be paid collectively by the three co-defendants in full satisfaction of all claims resulting in a dismissal of the case with prejudice and the resolution of (i) all pending and future claims by the plaintiffs in the case, and (ii) all potential claims for contribution or indemnity between NL and its co-defendants in respect to the case.
Number of Defendant | Defendant	3
Settlement amount	$ 305,000,000
Litigation settlement	101,700,000			$ 62,000,000
Litigation settlement charge upon approval of settlement terms	25,000,000.0			45,000,000
Remaining litigation settlement charge	$ 76,700,000		101,700,000	$ 20,000,000
Number of annual installments | Installment	6			5
Remaining litigation settlement charge due in first installment	$ 12,000,000.0
Remaining litigation settlement charge due in second installment	12,000,000.0
Remaining litigation settlement charge due in third installment	12,000,000.0
Remaining litigation settlement charge due in fourth installment	12,000,000.0
Remaining litigation settlement charge due in fifth installment	12,000,000.0
Remaining litigation settlement charge due in sixth installment	$ 16,700,000
Litigation settlement, current		$ 300,000		$ 80,000,000
Litigation settlement net present value			$ 96,300,000	$ 17,000,000
Litigation settlement installments payment beginning term from approval				4 years
Discounted rate for estimated present value of remaining litigation amount			1.90%
Litigation settlement expense, net			$ 19,600,000					$ 19,300,000
Litigation settlement, first annual installment payment							$ 12,000,000.0
Litigation settlement accrual payments		25,000,000.0
Accretion expense					$ 600,000	$ 1,300,000
California Lead Paint Litigation | NL | Other Assets
Commitments And Contingent Liabilities [Line Items]
Escrow deposit		$ 9,000,000.0