Litigation and Contingencies - Additional Information (Detail) $ in Millions	1 Months Ended	6 Months Ended
	Sep. 30, 2016 USD ($) Recipient entity	Jun. 30, 2021 USD ($) Recipient alternative entity mi	Aug. 07, 2020 USD ($)	Sep. 30, 2018 party	Feb. 28, 2015 USD ($)	Apr. 11, 2014 USD ($)
Loss Contingencies [Line Items]
Environmental remediation expense		$ 40.0
Number of general notice letter recipients | entity		100
Miles of river included in the remedial investigation and feasibility study | mi		8.3
Number of remediation alternatives | alternative		4
Number Of PRPs (in recipients) | Recipient	20
Number of public entities (in entities) | entity	5
Standby letters of credit outstanding		$ 52.0
Minimum
Loss Contingencies [Line Items]
Loss contingency, estimate of possible loss		1.0
Maximum
Loss Contingencies [Line Items]
Loss contingency, estimate of possible loss		$ 2.0
Lower Passaic River Matter
Loss Contingencies [Line Items]
Number of general notice letter recipients involved in remedial investigation and feasibility study | Recipient		72
Loss contingency estimated period		30 years
Number of parties sued (in parties) | party				120
Lower Passaic River Matter | Minimum
Loss Contingencies [Line Items]
Loss contingency, estimate of possible loss						$ 315.0
Lower Passaic River Matter | Maximum
Loss Contingencies [Line Items]
Loss contingency, estimate of possible loss						$ 3,200.0
Lower Passaic River Matter - Preferred Alternative
Loss Contingencies [Line Items]
Loss contingency, estimate of possible loss		$ 1,700.0
Lower Passaic River Matter - Preferred Alternative Maintenance Costs
Loss Contingencies [Line Items]
Loss contingency, estimate of possible loss		$ 2.0
Lower Passaic River Matter - Alternative Range from Participating Parties
Loss Contingencies [Line Items]
Miles of river included in the remedial investigation and feasibility study | mi		9
Lower Passaic River Matter - Alternative Range from Participating Parties | Minimum
Loss Contingencies [Line Items]
Loss contingency, estimate of possible loss			$ 321.0		$ 28.0
Lower Passaic River Matter - Alternative Range from Participating Parties | Maximum
Loss Contingencies [Line Items]
Loss contingency, estimate of possible loss			$ 468.0		$ 2,700.0
Lower Passaic River Matter - Selected Remedy for the Preferred Alternative
Loss Contingencies [Line Items]
Settlement amount	$ 0.3	$ 1,400.0
Lower half of river
Loss Contingencies [Line Items]
Miles of river included in the remedial investigation and feasibility study | mi		17