Note 13 - Guarantor Subsidiaries - Unaudited Interim Condensed Consolidating Statements of Operations (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Revenues	$ 136,925	$ 152,617
Cost of sales	(85,887)	(110,386)
Depreciation, depletion, amortization	(39,666)	(38,787)
General and administrative	(8,939)	(9,959)
Exploration and pre-development	(3,065)	(5,258)
Gain on derivative contracts	7,893	(1,799)
Acquisition costs	(5)	(13)
Equity in earnings of subsidiaries	0	0
Other (expense) income	(25,503)	(18,761)
(Loss) income before income taxes	(18,247)	(32,749)
Benefit (provision) from income taxes	1,062	7,216
Net (loss) income	(17,185)	(25,533)
Series B Preferred Stock dividends declared	(138)	(138)
(Loss) income applicable to common stockholders	(17,323)	(25,671)
Changes in comprehensive (loss) income	(19,335)	4,259
Comprehensive (loss) income	(36,520)	(21,274)
Research and development	0	(403)
Gain (loss) on derivative contracts	7,893	(1,799)
Reportable Legal Entities [Member] | Parent Company [Member]
Revenues	1,679	(2,477)
Cost of sales	(284)	(461)
Depreciation, depletion, amortization	0	0
General and administrative	(3,163)	(4,393)
Exploration and pre-development	(12)	(16)
Gain on derivative contracts	7,893	(1,799)
Acquisition costs	(5)	42
Equity in earnings of subsidiaries	11,330	(22,432)
Other (expense) income	(34,623)	6,003
(Loss) income before income taxes	(17,185)	(25,533)
Benefit (provision) from income taxes	0	0
Net (loss) income	(17,185)	(25,533)
Series B Preferred Stock dividends declared	(138)	(138)
(Loss) income applicable to common stockholders	(17,323)	(25,671)
Changes in comprehensive (loss) income	(19,335)	4,259
Comprehensive (loss) income	(36,520)	(21,274)
Research and development		0
Gain (loss) on derivative contracts	7,893	(1,799)
Reportable Legal Entities [Member] | Guarantor Subsidiaries [Member]
Revenues	125,316	142,494
Cost of sales	(78,751)	(99,333)
Depreciation, depletion, amortization	(38,193)	(37,027)
General and administrative	(5,339)	(5,111)
Exploration and pre-development	(2,055)	(3,062)
Gain on derivative contracts	0	0
Acquisition costs	0	(55)
Equity in earnings of subsidiaries	0	0
Other (expense) income	10,704	(19,778)
(Loss) income before income taxes	11,682	(22,275)
Benefit (provision) from income taxes	1,056	(62)
Net (loss) income	12,738	(22,337)
Series B Preferred Stock dividends declared	0	0
(Loss) income applicable to common stockholders	12,738	(22,337)
Changes in comprehensive (loss) income	0	0
Comprehensive (loss) income	12,738	(22,337)
Research and development		(403)
Gain (loss) on derivative contracts	0	0
Reportable Legal Entities [Member] | Non-Guarantor Subsidiaries [Member]
Revenues	9,930	12,600
Cost of sales	(6,852)	(10,592)
Depreciation, depletion, amortization	(1,473)	(1,760)
General and administrative	(437)	(455)
Exploration and pre-development	(998)	(2,180)
Gain on derivative contracts	0	0
Acquisition costs	0	0
Equity in earnings of subsidiaries	0	0
Other (expense) income	(741)	1,407
(Loss) income before income taxes	(571)	(980)
Benefit (provision) from income taxes	(837)	885
Net (loss) income	(1,408)	(95)
Series B Preferred Stock dividends declared	0	0
(Loss) income applicable to common stockholders	(1,408)	(95)
Changes in comprehensive (loss) income	0	0
Comprehensive (loss) income	(1,408)	(95)
Research and development		0
Gain (loss) on derivative contracts	0	0
Consolidation, Eliminations [Member]
Revenues	0	0
Cost of sales	0	0
Depreciation, depletion, amortization	0	0
General and administrative	0	0
Exploration and pre-development	0	0
Gain on derivative contracts	0	0
Acquisition costs	0	0
Equity in earnings of subsidiaries	(11,330)	22,432
Other (expense) income	(843)	(6,393)
(Loss) income before income taxes	(12,173)	16,039
Benefit (provision) from income taxes	843	6,393
Net (loss) income	(11,330)	22,432
Series B Preferred Stock dividends declared	0	0
(Loss) income applicable to common stockholders	(11,330)	22,432
Changes in comprehensive (loss) income	0	0
Comprehensive (loss) income	(11,330)	22,432
Research and development		0
Gain (loss) on derivative contracts	$ 0	$ 0