Discontinued Operations - Summary of Revenue and Loss before Income Taxes Attributable to Discontinued Operations (Detail) - USD ($)	3 Months Ended
Mar. 31, 2019	Mar. 31, 2018
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Loss from discontinued operations, net of taxes		$ (35,000)
Petroleum Segment [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Operating expenses	$ 1,000	47,000
Loss from discontinued operations before income taxes	(1,000)	(47,000)
Income tax (benefit)	$ (1,000)	(12,000)
Loss from discontinued operations, net of taxes		$ (35,000)

Amount before tax of income (loss) from a discontinued operation. Includes, but is not limited to, the income (loss) from operations during the phase-out period, gain (loss) on disposal, gain (loss) for reversal of write-down (write-down) to fair value, less cost to sell, and adjustments to a prior period gain (loss) on disposal.

Amount of tax expense (benefit) related to a discontinued operation. Includes, but is not limited to, tax expense (benefit) related to income (loss) from operations during the phase-out period, tax expense (benefit) related to gain (loss) on disposal, tax expense (benefit) related to gain (loss) for reversal of write-down (write-down) to fair value, less cost to sell, and tax expense (benefit) related to adjustments of a prior period gain (loss) on disposal.

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