Commitments and Contingencies - Lead Pigment Litigation-NL and Environmental Matters and Litigation - Additional Information (Detail) $ in Millions		3 Months Ended		6 Months Ended		9 Months Ended
	Jul. 24, 2019 USD ($) Defendant Installment	Sep. 30, 2019 USD ($) site	Jun. 30, 2019 USD ($)	Jun. 30, 2019 USD ($)	Jun. 30, 2018 USD ($) Installment	Sep. 30, 2019 USD ($) Cases Installment site	Sep. 30, 2018 USD ($)	Dec. 31, 2018 USD ($)	Nov. 30, 2018 Complaint
Commitments And Contingent Liabilities [Line Items]
Litigation settlement		$ 11.8				$ 11.8		$ 60.0
Litigation settlement net present value		59.8				59.8		17.0
Litigation settlement expense, net		(0.3)				19.3	$ 62.0
Accrued litigation settlement		59.8				59.8		17.0
Current insurance recovery receivable		0.0				0.0		15.0
Accrual for reasonably estimable environmental remediation and related matters		100.0				100.0		$ 103.4
Other Environmental Cleanup Matters
Commitments And Contingent Liabilities [Line Items]
Accrual for reasonably estimable environmental remediation and related matters		5.0				5.0
NL
Commitments And Contingent Liabilities [Line Items]
Number of complaints filed | Complaint									2
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		$ 95.0				$ 95.0
Number of sites associated with remediation and related costs | site		32				32
Number of sites for which NL not currently able to reasonably estimate range of costs | site		5				5
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		$ 115.0				$ 115.0
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
Commitments And Contingent Liabilities [Line Items]
Litigation settlement		11.8				$ 11.8
Litigation settlement net present value		59.8				59.8
Litigation settlement due in 2020		12.0				12.0
Accrued litigation settlement		59.8				59.8
Insurance recovery receivable noncurrent		15.6				15.6
Escrow Deposit		9.0				$ 9.0
California Lead Paint Litigation | Aggregate Net Present Value of Five Payments
Commitments And Contingent Liabilities [Line Items]
Number of remaining annual installments | Installment						5
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	$ 305.0
Litigation settlement	101.7				$ 62.0
Litigation settlement charge upon approval of settlement terms	25.0				45.0
Remaining litigation settlement charge	$ 76.7		$ 101.7	$ 101.7	$ 20.0
Number of annual installments | Installment	6				5
Remaining litigation settlement charge due in first installment	$ 12.0
Remaining litigation settlement charge due in second installment	12.0
Remaining litigation settlement charge due in third installment	12.0
Remaining litigation settlement charge due in fourth installment	12.0
Remaining litigation settlement charge due in fifth installment	12.0
Remaining litigation settlement charge due in sixth installment	$ 16.7
Litigation settlement, current					$ 80.0
Litigation settlement net present value			$ 96.3	$ 96.3	$ 17.0
Litigation settlement installments payment beginning term from approval					4 years
Discounted rate for estimated present value of remaining litigation amount			1.90%	1.90%
Litigation settlement expense, net		3.0	$ 19.6	$ 19.3
Litigation settlement accrual payments		25.0				$ 25.0
Accretion expense		$ 3.0
Accrued litigation settlement			$ 96.3	$ 96.3	$ 17.0