Segment Reporting - Reconciliation of Segment Earnings to Earnings Before Income Taxes (Details) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Reconciliation of Operating Profit (Loss) from Segments to Consolidated [Abstract]
Operating (losses) earnings	$ 2,935	$ (643)	$ (17,005)	$ 4,610
Gain on dissolution of investment	0	75	0	573
Interest income	144	731	509	1,387
Interest expense	(68)	(117)	(218)	(182)
(Losses) Earnings before income taxes	3,011	46	(16,714)	6,388
Operating Segments
Reconciliation of Operating Profit (Loss) from Segments to Consolidated [Abstract]
Operating (losses) earnings	5,666	1,939	(11,380)	9,876
General and administrative
Reconciliation of Operating Profit (Loss) from Segments to Consolidated [Abstract]
Operating (losses) earnings	(2,731)	(2,582)	(5,625)	(5,266)
Segment reconciling items
Reconciliation of Operating Profit (Loss) from Segments to Consolidated [Abstract]
Gain on dissolution of investment	0	75	0	573
Interest income	144	731	509	1,387
Interest expense	$ (68)	$ (117)	$ (218)	$ (182)

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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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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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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