Note 13 - Guarantor Subsidiaries - Unaudited Interim Condensed Consolidating Statements of Operations (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Revenues	$ 142,544	$ 131,017
Cost of sales	(78,676)	(74,320)
Depreciation, depletion, amortization	(28,952)	(25,875)
General and administrative	(9,206)	(10,214)
Exploration and pre-development	(5,766)	(3,354)
Loss on derivative contracts	(7,809)
Other (expense) income	(14,372)	(16,218)
Income (loss) before income taxes	(2,237)	1,036
Income tax benefit (provision)	29,071	(1,654)
Net income (loss)	26,834	(618)
Preferred stock dividends	(138)	(138)
Income (loss) applicable to common stockholders	26,696	(756)
Changes in comprehensive income (loss)	3,204	1,065
Comprehensive income (loss)	30,038	447
Consolidation, Eliminations [Member]
Revenues
Cost of sales
Depreciation, depletion, amortization
General and administrative
Exploration and pre-development
Loss on derivative contracts
Equity in earnings of subsidiaries	(2,701)	20,991
Other (expense) income	(44,820)	(16,829)
Income (loss) before income taxes	(47,521)	4,162
Income tax benefit (provision)	44,820	16,829
Net income (loss)	(2,701)	20,991
Preferred stock dividends
Income (loss) applicable to common stockholders	(2,701)	20,991
Changes in comprehensive income (loss)	89	(1,068)
Comprehensive income (loss)	(2,612)	19,923
Parent Company [Member] | Reportable Legal Entities [Member]
Revenues	(4,093)	(6,135)
Cost of sales	(148)
Depreciation, depletion, amortization
General and administrative	(6,469)	(5,240)
Exploration and pre-development	(244)	(45)
Loss on derivative contracts	(7,809)
Equity in earnings of subsidiaries	2,701	(20,991)
Other (expense) income	42,896	31,793
Income (loss) before income taxes	26,834	(618)
Income tax benefit (provision)
Net income (loss)	26,834	(618)
Preferred stock dividends	(138)	(138)
Income (loss) applicable to common stockholders	26,696	(756)
Changes in comprehensive income (loss)	3,204	1,065
Comprehensive income (loss)	30,038	447
Guarantor Subsidiaries [Member] | Reportable Legal Entities [Member]
Revenues	82,953	81,269
Cost of sales	(42,772)	(46,753)
Depreciation, depletion, amortization	(15,766)	(16,606)
General and administrative	(2,319)	(4,523)
Exploration and pre-development	(1,901)	(1,287)
Loss on derivative contracts
Equity in earnings of subsidiaries
Other (expense) income	(3,116)	4,336
Income (loss) before income taxes	17,079	16,436
Income tax benefit (provision)	(8,969)	(4,833)
Net income (loss)	8,110	11,603
Preferred stock dividends
Income (loss) applicable to common stockholders	8,110	11,603
Changes in comprehensive income (loss)		8
Comprehensive income (loss)	8,110	11,611
Non-Guarantor Subsidiaries [Member] | Reportable Legal Entities [Member]
Revenues	63,684	55,883
Cost of sales	(35,756)	(27,567)
Depreciation, depletion, amortization	(13,186)	(9,269)
General and administrative	(418)	(451)
Exploration and pre-development	(3,621)	(2,022)
Loss on derivative contracts
Equity in earnings of subsidiaries
Other (expense) income	(9,332)	(35,518)
Income (loss) before income taxes	1,371	(18,944)
Income tax benefit (provision)	(6,780)	(13,650)
Net income (loss)	(5,409)	(32,594)
Preferred stock dividends
Income (loss) applicable to common stockholders	(5,409)	(32,594)
Changes in comprehensive income (loss)	(89)	1,060
Comprehensive income (loss)	$ (5,498)	$ (31,534)