Commitments and Contingent Liabilities - Additional Information (Detail) $ in Millions, $ in Millions	3 Months Ended	12 Months Ended
	Mar. 31, 2020 USD ($) State Plaintiff Case site Party Plant	Dec. 31, 2019 USD ($) Plaintiff Case	Oct. 10, 2019 USD ($)	Oct. 10, 2019 AUD ($)	Dec. 31, 2018 USD ($)
Loss Contingencies [Line Items]
Number of states with new claims filed | State	2
Number of plaintiffs | Plaintiff	64	64
Environmental remediation and regulation liability	$ 9.3	$ 9.5			$ 10.1
Accrued liability for environmental matters, current	2.7	2.8
Environment Protection Authority [Member]
Loss Contingencies [Line Items]
Reserve for legal proceedings	2.8
Portland Harbor and Newark Bay CERCLA sites [Member]
Loss Contingencies [Line Items]
Costs of participating in PRP group	$ 2.2
Beazer East [Member]
Loss Contingencies [Line Items]
Sites listed on National Priorities List | site	1
Compensatory Damages [Member]
Loss Contingencies [Line Items]
Number of cases | Case	34
Punitive Damages [Member]
Loss Contingencies [Line Items]
Number of cases | Case	29
Indemnification Agreement [Member] | Beazer East [Member]
Loss Contingencies [Line Items]
Environmental remediation costs paid by others, per year		$ 10.5
Coal Tar Pitch Cases [Member]
Loss Contingencies [Line Items]
Number of cases | Case	34	34
Pennsylvania [Member]
Loss Contingencies [Line Items]
Number of cases | Case	33
Pennsylvania [Member] | Coal Tar Pitch Cases [Member]
Loss Contingencies [Line Items]
Number of cases | Case	33
Tennessee [Member] | Coal Tar Pitch Cases [Member]
Loss Contingencies [Line Items]
Number of cases | Case	1
Compensatory damages	$ 15.0
Oregon [Member]
Loss Contingencies [Line Items]
Number of potential responsible parties | Party	80
Oregon [Member] | Environment Protection Authority [Member]
Loss Contingencies [Line Items]
Net present value of selected remedy estimation	$ 1,100.0
Undiscounted cost of selected remedy estimation	1,700.0
United States [Member]
Loss Contingencies [Line Items]
Environmental remediation and regulation liability	$ 4.3
United States [Member] | Performance Chemicals [Member]
Loss Contingencies [Line Items]
Number of plant sites | Plant	2
United States [Member] | Utility and Industrial Products [Member]
Loss Contingencies [Line Items]
Number of plant sites | Plant	1
New South Wales [Member] | Environment Protection Authority [Member]
Loss Contingencies [Line Items]
Reserve for legal proceedings			$ 0.7	$ 1.0
Australia [Member] | Performance Chemicals [Member]
Loss Contingencies [Line Items]
Environmental remediation and regulation liability	$ 1.2