Commitments and Contingencies - Additional Information (Detail)				1 Months Ended	9 Months Ended		12 Months Ended
	Oct. 05, 2016	Mar. 04, 2016 USD ($)	Jul. 07, 2014 Defendant	May 31, 2007 Defendant	Sep. 30, 2016 USD ($) Parties Defendant	Sep. 30, 2015 USD ($)	Dec. 31, 2015 USD ($)	Sep. 30, 2003 Parties
Loss Contingencies [Line Items]
Accrued legal matters					$ 11,767,000		$ 11,265,000
Provisions for litigation losses					$ 801,000	$ 349,000
8 Mile Stretch of Lower Passaic River [Member]
Loss Contingencies [Line Items]
Cost estimate for remediating Lower Passaic River		$ 1,380,000,000
Minimum [Member] | 17 Mile Stretch of Lower Passaic River [Member]
Loss Contingencies [Line Items]
Cost estimate for remediating Lower Passaic River							483,000,000
Maximum [Member] | 17 Mile Stretch of Lower Passaic River [Member]
Loss Contingencies [Line Items]
Cost estimate for remediating Lower Passaic River							$ 725,000,000
Occidental Chemical Corporation [Member] | Subsequent Event [Member] | EPA [Member]
Loss Contingencies [Line Items]
Remedial design performance period under EPA settlement agreement	4 years
Lower Passaic River [Member]
Loss Contingencies [Line Items]
Number of potentially responsible parties for Lower Passaic River damages | Parties								66
Parties to perform a remedial investigation and feasibility study | Defendant				70
Lower Passaic River [Member] | Minimum [Member]
Loss Contingencies [Line Items]
Number of potentially responsible parties for Lower Passaic River damages | Parties					100
NJ | MTBE [Member]
Loss Contingencies [Line Items]
Number of defendants in the MTBE complaint | Defendant					50
PA | MTBE [Member] | Minimum [Member]
Loss Contingencies [Line Items]
Number of defendants in the MTBE complaint | Defendant			50