Segment Reporting - Reconciliation of Segment Earnings to Earnings Before Income Taxes (Details) - USD ($) $ in Thousands	1 Months Ended	3 Months Ended	9 Months Ended
Aug. 31, 2017	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Reconciliation of Operating Profit (Loss) from Segments to Consolidated [Abstract]
Operating earnings (losses)		$ 2,239	$ (1,290)	$ 7,614	$ (2,255)
Loss on deconsolidation of subsidiary		0	(1,870)	0	(3,505)
Impairment of investment in unconsolidated affiliate		0	(2,500)	0	(2,500)
Interest income		601	370	1,486	789
Interest expense		(26)	(8)	(60)	(10)
(Losses) earnings before income taxes		2,814	(5,298)	9,040	(7,481)
Voluntary early retirement program expense	$ 400		1,000		1,000
Reporting Segments
Reconciliation of Operating Profit (Loss) from Segments to Consolidated [Abstract]
Operating earnings (losses)		3,772	1,497	13,714	4,629
General and administrative
Reconciliation of Operating Profit (Loss) from Segments to Consolidated [Abstract]
Operating earnings (losses)		(1,533)	(2,787)	(6,100)	(6,884)
Segment reconciling items
Reconciliation of Operating Profit (Loss) from Segments to Consolidated [Abstract]
Loss on deconsolidation of subsidiary		0	(1,870)	0	(3,505)
Impairment of investment in unconsolidated affiliate		0	2,500	0	2,500
Interest income		601	370	1,486	789
Interest expense		$ (26)	$ (8)	$ (60)	$ (10)

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- Definition

Amount of gain (loss) from deconsolidation of subsidiary and derecognition of group of assets constituting transfer of business or nonprofit activity, excluding conveyance of oil and gas mineral rights and transfer of good or service in contract with customer.

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This item represents an other than temporary decline in value that has been recognized against an investment accounted for under the equity method of accounting. The excess of the carrying amount over the fair value of the investment represents the amount of the write down which is or was reflected in earnings. The written down value is a new cost basis with the adjusted value of the investment becoming its new carrying value subject to the equity accounting method. Evidence of a loss in value might include, but would not necessarily be limited to, absence of an ability to recover the carrying amount of the investment or inability of the investee to sustain an earnings capacity which would justify the carrying amount of the investment.

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Amount of income (loss) from continuing operations before deduction of income tax expense (benefit) and income (loss) attributable to noncontrolling interest, and addition of income (loss) from equity method investments.

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- Definition

Amount of the cost of borrowed funds accounted for as interest expense.

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Amount before accretion (amortization) of purchase discount (premium) of interest income on nonoperating securities.

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The net result for the period of deducting operating expenses from operating revenues.

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