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Commitments and Contingencies - Additional Information (Detail) |  |  |  |  | 1 Months Ended | 6 Months Ended | 12 Months Ended |  |  |  |
--- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | ---
Dec. 17, 2017 Defendant | Oct. 05, 2016 | Mar. 04, 2016 USD ($) | Jul. 07, 2014 Defendant | May 31, 2007 Defendant | Jun. 30, 2018 USD ($) Defendant | Dec. 31, 2015 USD ($) | Jan. 31, 2018 USD ($) Party | Dec. 31, 2017 USD ($) | Mar. 30, 2017 Party | Sep. 30, 2003 Party
Loss Contingencies [Line Items] |  |  |  |  |  |  |  |  |  |  |
Accrued legal matters |  |  |  |  |  | $ 12,311,000 |  |  | $ 12,311,000 |  |
Litigation losses |  |  |  |  |  | (70,000) |  |  |  |  |
Legal litigation settlements |  |  |  |  |  | $ 147,000 |  |  |  |  |
Occidental Chemical Corporation [Member] | EPA [Member] |  |  |  |  |  |  |  |  |  |  |
Loss Contingencies [Line Items] |  |  |  |  |  |  |  |  |  |  |
Number of potentially responsible parties | Party |  |  |  |  |  |  |  |  |  | 20 |
Remedial design performance period under EPA settlement agreement |  | 4 years |  |  |  |  |  |  |  |  |
Number of potentially responsible parties that the EPA intends to enter into a final settlement agreement with | Party |  |  |  |  |  |  |  | 15 |  |  |
Remediation cost for identified responsible parties |  |  |  |  |  |  |  | $ 280,600 |  |  |
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] | Occidental Chemical Corporation [Member] | CERCLA [Member] |  |  |  |  |  |  |  |  |  |  |
Loss Contingencies [Line Items] |  |  |  |  |  |  |  |  |  |  |
Number of defendants under complaint | Defendant |  |  |  |  |  | 120 |  |  |  |  |
Maximum [Member] | 17 Mile Stretch of Lower Passaic River [Member] |  |  |  |  |  |  |  |  |  |  |
Loss Contingencies [Line Items] |  |  |  |  |  |  |  |  |  |  |
Cost estimate for remediating Lower Passaic River |  |  |  |  |  |  | $ 725,000,000 |  |  |  |
Lower Passaic River [Member] |  |  |  |  |  |  |  |  |  |  |
Loss Contingencies [Line Items] |  |  |  |  |  |  |  |  |  |  |
Number of potentially responsible parties | Party |  |  |  |  |  |  |  |  |  |  | 66
Lower Passaic River [Member] | Minimum [Member] |  |  |  |  |  |  |  |  |  |  |
Loss Contingencies [Line Items] |  |  |  |  |  |  |  |  |  |  |
Parties to perform a remedial investigation and feasibility study | Defendant |  |  |  |  | 70 |  |  |  |  |  |
MTBE [Member] | NJ [Member] |  |  |  |  |  |  |  |  |  |  |
Loss Contingencies [Line Items] |  |  |  |  |  |  |  |  |  |  |
Number of defendants in the MTBE complaint | Defendant |  |  |  |  |  | 50 |  |  |  |  |
MTBE [Member] | Minimum [Member] | PA [Member] |  |  |  |  |  |  |  |  |  |  |
Loss Contingencies [Line Items] |  |  |  |  |  |  |  |  |  |  |
Number of defendants in the MTBE complaint | Defendant |  |  |  | 50 |  |  |  |  |  |  |
MTBE [Member] | Minimum [Member] | MARYLAND [Member] |  |  |  |  |  |  |  |  |  |  |
Loss Contingencies [Line Items] |  |  |  |  |  |  |  |  |  |  |
Number of defendants in the MTBE complaint | Defendant | 60 |  |  |  |  |  |  |  |  |  |

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