Discontinued Operations - Additional Information (Detail) - USD ($)		1 Months Ended				3 Months Ended		12 Months Ended
	Feb. 10, 2017	Apr. 30, 2019	Feb. 28, 2019	May 31, 2018	Feb. 28, 2018	Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2018	Dec. 31, 2017
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Proceeds from sale of assets						$ 862,000	$ 862,000
Environmental Incident 1994 [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Additional remediation costs accrued								$ 56,000
Environmental remediation						470,000		490,000	$ 434,000
Costs incurred related to environmental remediation						$ 20,000		$ 111,000
Sale of Petroleum Segment [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Reduced sales price	$ 1,040,000			$ 1,040,000
Estimated cost of the project				$ 1,923,284
Percentage of obligation on cost in excess of estimated cost				50.00%
Entities obligation on cost in excess of initial estimated cost				$ 441,642
Maximum additional obligation				$ 104,000
Escrow deposit release			$ 862,000		$ 862,000
Percentage Of Escrow Deposit Receivable, After twelve months			50.00%		50.00%
Interest income			$ 23,000
Sale of Petroleum Segment [Member] | Subsequent Event [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Estimated cost of the project		$ 1,923,284
Maximum additional obligation		$ 104,000
Terminal [Member] | Sale of Petroleum Segment [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Sales price	23,000,000
Reduced sales price	1,040,000
Amount of purchase price held in escrow	1,725,000
Other expenses related to sales agreement	441,000
Proceeds from sale of assets	$ 19,800,000