CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Revenues:
Total revenues	$ 1,750,213	$ 1,322,060	$ 1,099,540
Costs and expenses:
Oil and natural gas property impairments	0	3	313
General and administrative	8,937	9,707	10,410
Depreciation, depletion and amortization	10,654	13,599	18,792
Total costs and expenses	1,748,805	1,320,558	1,093,486
Operating earnings (losses)	1,408	1,502	6,054
Other income (expense):
Loss on deconsolidation of subsidiary (Note 4)	0	(3,505)	0
Impairment of investment in unconsolidated affiliate	0	(2,500)	0
Interest income	2,155	1,103	582
Interest expense	(109)	(27)	(2)
Total other income (expense), net	2,046	(4,929)	580
(Losses) earnings before income taxes and investment in unconsolidated affiliate	3,454	(3,427)	6,634
Income tax (provision) benefit:
Current	427	(895)	(2,778)
Deferred	(936)	3,840	87
Income tax benefit (provision)	(509)	2,945	(2,691)
Earnings (losses) from continuing operations	2,945	(482)	3,943
Losses from investments in unconsolidated affiliates, net of tax benefit of $—, $—, and $770, respectively	0	0	(1,430)
Net (losses) earnings	$ 2,945	$ (482)	$ 2,513
Basic earnings (losses) per common share:
From continuing operations (in dollars per share)	$ 0.70	$ (0.11)	$ 0.94
From investment in unconsolidated affiliate (in dollars per share)	0	0	(0.34)
Basic net (losses) earnings per common share (in dollars per share)	0.70	(0.11)	0.60
Diluted net (losses) earnings per common share (in dollars per share)	0.70	(0.11)	0.60
Dividends per common share (in dollars per share)	$ 0.88	$ 0.88	$ 0.88
Marketing
Revenues:
Total revenues	$ 1,694,437	$ 1,267,275	$ 1,043,775
Costs and expenses:
Cost and expenses	1,681,045	1,247,763	1,016,733
Transportation
Revenues:
Total revenues	55,776	53,358	52,355
Costs and expenses:
Cost and expenses	48,169	48,538	45,154
Oil and natural gas
Revenues:
Total revenues	0	1,427	3,410
Costs and expenses:
Cost and expenses	$ 0	$ 948	$ 2,084