Subsidiary Guarantors - Condensed Consolidating Statement of Operations (Details) - USD ($) $ in Thousands	3 Months Ended			6 Months Ended	9 Months Ended
	Sep. 30, 2017	Jun. 30, 2017	Sep. 30, 2016	Jun. 30, 2017	Sep. 30, 2017	Sep. 30, 2016
Operating revenues
Oil and gas sales	$ 43,636		$ 32,582		$ 132,427	$ 86,060
Other revenues	566		771		1,634	2,295
Total operating revenues	44,202		33,353		134,061	88,355
Operating costs and expenses
Lease operating	9,458		7,865		27,689	24,027
Production and ad valorem taxes	2,757		1,733		4,641	5,061
Exploration	1,969		998		11,638	1,237
Depletion, depreciation and amortization	46,353		36,550		127,343	116,449
Impairment of oil and gas properties		$ 148,016		$ 148,016	148,016
Accretion of ARO liability	253		323		720	913
General and administrative	7,819		6,448		24,493	22,078
Total operating expenses	68,609	221,191	53,917	275,931	344,540	169,765
Operating income (loss)	(24,407)	(172,565)	(20,564)	(186,072)	(210,479)	(81,410)
Other income (expense)
Interest expense	(12,817)		(12,792)		(38,381)	(40,397)
Gain on debt extinguishment						99,530
Net gain (loss) on commodity derivatives	(32,539)		4,014		11,308	(18,769)
Other income (expense)	(13,692)	27,501	364	28,081	14,389	251
Other income (expense), net	(59,048)	36,351	(8,414)	46,364	(12,684)	40,615
Income (loss) before income tax	(83,455)	(136,214)	(28,978)	(139,708)	(223,163)	(40,795)
Income tax provision (benefit)	(492)	(2,236)	(6,549)	(2,215)	(2,707)	(8,234)
Net income (loss)	(82,963)	(133,978)	(22,429)	(137,493)	(220,456)	(32,561)
Net income (loss) attributable to non-controlling interests	(18,157)	(51,762)	(12,576)	(53,890)	(72,047)	(18,374)
Net income (loss) attributable to controlling interests	(64,806)	(82,216)	(9,853)	(83,603)	(148,409)	(14,187)
Dividends and accretion on preferred stock	(1,966)		(765)		(5,959)	(765)
Net income (loss) attributable to common shareholders	(66,772)	$ (84,182)	(10,618)	$ (87,596)	(154,368)	(14,952)
Eliminations
Other income (expense)
Equity interest in income	71,038		29,239		238,993	41,218
Net income (loss)	71,038		29,239		238,993	41,218
Net income (loss) attributable to non-controlling interests	(18,157)		(12,576)		(72,047)	(18,374)
Net income (loss) attributable to controlling interests	89,195		41,815		311,040	59,592
Net income (loss) attributable to common shareholders	89,195		41,815		311,040	59,592
JEI (Parent)
Other income (expense)
Other income (expense)	(12,417)		261		15,831	423
Other income (expense), net	(12,417)		261		15,831	423
Income (loss) before income tax	(12,417)		261		15,831	423
Equity interest in income	(52,955)		(15,999)		(167,027)	(22,130)
Income tax provision (benefit)	(566)		(5,885)		(2,787)	(7,520)
Net income (loss)	(64,806)		(9,853)		(148,409)	(14,187)
Net income (loss) attributable to controlling interests	(64,806)		(9,853)		(148,409)	(14,187)
Dividends and accretion on preferred stock	(1,966)		(765)		(5,959)	(765)
Net income (loss) attributable to common shareholders	(66,772)		(10,618)		(154,368)	(14,952)
Issuers
Operating revenues
Other revenues	475		587		1,417	1,828
Total operating revenues	475		587		1,417	1,828
Operating costs and expenses
General and administrative	3,044		2,928		8,957	8,782
Total operating expenses	3,044		2,928		8,957	8,782
Operating income (loss)	(2,569)		(2,341)		(7,540)	(6,954)
Other income (expense)
Interest expense	(12,917)		(12,652)		(38,673)	(40,417)
Gain on debt extinguishment						99,530
Net gain (loss) on commodity derivatives	(32,539)		4,014		11,308	(18,769)
Other income (expense)	(25)		(25)		(72)	(298)
Other income (expense), net	(45,481)		(8,663)		(27,437)	40,046
Income (loss) before income tax	(48,050)		(11,004)		(34,977)	33,092
Equity interest in income	(18,083)		(13,240)		(71,966)	(19,088)
Income tax provision (benefit)	74		(664)		80	(714)
Net income (loss)	(66,207)		(23,580)		(107,023)	14,718
Net income (loss) attributable to controlling interests	(66,207)		(23,580)		(107,023)	14,718
Net income (loss) attributable to common shareholders	(66,207)		(23,580)		(107,023)	14,718
Guarantor Subsidiaries
Operating revenues
Oil and gas sales	43,636		32,582		132,427	86,060
Other revenues	91		184		217	467
Total operating revenues	43,727		32,766		132,644	86,527
Operating costs and expenses
Lease operating	9,458		7,865		27,689	24,027
Production and ad valorem taxes	2,757		1,733		4,641	5,061
Exploration	1,969		998		11,638	1,237
Depletion, depreciation and amortization	46,330		36,527		127,275	116,385
Impairment of oil and gas properties					148,016
Accretion of ARO liability	253		323		720	913
General and administrative	4,705		3,476		15,336	13,087
Total operating expenses	65,472		50,922		335,315	160,710
Operating income (loss)	(21,745)		(18,156)		(202,671)	(74,183)
Other income (expense)
Interest expense	100		(140)		292	20
Other income (expense)	(1,250)		128		(1,370)	126
Other income (expense), net	(1,150)		(12)		(1,078)	146
Income (loss) before income tax	(22,895)		(18,168)		(203,749)	(74,037)
Net income (loss)	(22,895)		(18,168)		(203,749)	(74,037)
Net income (loss) attributable to controlling interests	(22,895)		(18,168)		(203,749)	(74,037)
Net income (loss) attributable to common shareholders	(22,895)		(18,168)		(203,749)	(74,037)
Non-Guarantor Subsidiaries
Operating costs and expenses
Depletion, depreciation and amortization	23		23		68	64
General and administrative	70		44		200	209
Total operating expenses	93		67		268	273
Operating income (loss)	(93)		(67)		(268)	(273)
Other income (expense)
Income (loss) before income tax	(93)		(67)		(268)	(273)
Net income (loss)	(93)		(67)		(268)	(273)
Net income (loss) attributable to controlling interests	(93)		(67)		(268)	(273)
Net income (loss) attributable to common shareholders	$ (93)		$ (67)		$ (268)	$ (273)