Segment Reporting - Reconciliation of Segment Earnings to Earnings Before Income Taxes (Details) - USD ($) $ in Thousands	3 Months Ended
Mar. 31, 2021	Mar. 31, 2020
Reconciliation of Operating Profit (Loss) from Segments to Consolidated [Abstract]
Operating earnings (losses)	$ 3,851	$ (19,940)
General and administrative	(3,376)	(2,894)
Interest and other income	134	365
Interest expense	(220)	(150)
Earnings (Losses) before income taxes	3,765	(19,725)
Operating segments
Reconciliation of Operating Profit (Loss) from Segments to Consolidated [Abstract]
Operating earnings (losses)	7,227	(17,046)
General and administrative
Reconciliation of Operating Profit (Loss) from Segments to Consolidated [Abstract]
Operating earnings (losses)	0	0
General and administrative	(3,376)	(2,894)
Segment reconciling items
Reconciliation of Operating Profit (Loss) from Segments to Consolidated [Abstract]
Interest and other income	134	365
Interest expense	$ (220)	$ (150)

The aggregate total of expenses of managing and administering the affairs of an entity, including affiliates of the reporting entity, which are not directly or indirectly associated with the manufacture, sale or creation of a product or product line.

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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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The amount of interest income and other income recognized during the period. Included in this element is interest derived from investments in debt securities, cash and cash equivalents, and other investments which reflect the time value of money or transactions in which the payments are for the use or forbearance of money and other income from ancillary business-related activities (that is, excluding major activities considered part of the normal operations of the business).

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

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

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