Subsidiary Guarantors - Condensed Consolidating Statement of Cash Flows (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
Cash flows from operating activities
Net income (loss)	$ (82,963)	$ (133,978)	$ (22,429)	$ (137,493)	$ (220,456)	$ (32,561)
Adjustments to reconcile net income (loss) to net cash provided by operating activities					261,881	47,470
Net cash provided by operations				21,478	41,425	14,909
Cash flows from investing activities
Additions to oil and gas properties					(179,152)	(212,419)
Net adjustments to purchase price of properties acquired					2,391
Proceeds from sales of assets					60,422	1,615
Acquisition of other property, plant and equipment					(603)	(194)
Current period settlements of matured derivative contracts					69,412	106,151
Net cash (used in) investing					(47,530)	(104,847)
Cash flows from financing activities
Proceeds from issuance of long-term debt					102,000	75,000
Repayment of long-term debt					(129,000)	(42,000)
Purchase of senior notes						(84,589)
Payment of cash dividends on preferred stock					(3,367)
Net distributions paid to JEH unitholders					(562)	(10,109)
Net payments for share based compensation					(462)
Proceeds from sale of common stock					8,332	65,548
Proceeds from sale of preferred stock						88,236
Net cash (used in) / provided by financing					(23,059)	92,086
Net increase (decrease) in cash				(28,388)	(29,164)	2,148
Cash
Beginning of period	6,254			34,642	34,642	21,893
End of period	5,478	$ 6,254	24,041	6,254	5,478	24,041
Eliminations
Cash flows from operating activities
Net income (loss)	71,038		29,239		238,993	41,218
Adjustments to reconcile net income (loss) to net cash provided by operating activities					(238,993)	(41,218)
JEI (Parent)
Cash flows from operating activities
Net income (loss)	(64,806)		(9,853)		(148,409)	(14,187)
Adjustments to reconcile net income (loss) to net cash provided by operating activities					118,459	(134,592)
Net cash provided by operations					(29,950)	(148,779)
Cash flows from financing activities
Payment of cash dividends on preferred stock					(3,367)
Net distributions paid to JEH unitholders					1,075	9,910
Proceeds from sale of common stock					8,332	65,548
Proceeds from sale of preferred stock						88,236
Net cash (used in) / provided by financing					6,040	163,694
Net increase (decrease) in cash					(23,910)	14,915
Cash
Beginning of period				27,164	27,164	100
End of period	3,254		15,015		3,254	15,015
Issuers
Cash flows from operating activities
Net income (loss)	(66,207)		(23,580)		(107,023)	14,718
Adjustments to reconcile net income (loss) to net cash provided by operating activities					64,770	(53,206)
Net cash provided by operations					(42,253)	(38,488)
Cash flows from investing activities
Current period settlements of matured derivative contracts					69,412	106,151
Net cash (used in) investing					69,412	106,151
Cash flows from financing activities
Proceeds from issuance of long-term debt					102,000	75,000
Repayment of long-term debt					(129,000)	(42,000)
Purchase of senior notes						(84,589)
Net distributions paid to JEH unitholders					(1,637)	(20,019)
Net payments for share based compensation					(462)
Net cash (used in) / provided by financing					(29,099)	(71,608)
Net increase (decrease) in cash					(1,940)	(3,945)
Cash
Beginning of period				1,975	1,975	12,448
End of period	35		8,503		35	8,503
Guarantor Subsidiaries
Cash flows from operating activities
Net income (loss)	(22,895)		(18,168)		(203,749)	(74,037)
Adjustments to reconcile net income (loss) to net cash provided by operating activities					317,377	276,213
Net cash provided by operations					113,628	202,176
Cash flows from investing activities
Additions to oil and gas properties					(179,152)	(212,419)
Net adjustments to purchase price of properties acquired					2,391
Proceeds from sales of assets					60,422	1,615
Acquisition of other property, plant and equipment					(603)	(194)
Net cash (used in) investing					(116,942)	(210,998)
Cash flows from financing activities
Net increase (decrease) in cash					(3,314)	(8,822)
Cash
Beginning of period				5,483	5,483	9,325
End of period	2,169		503		2,169	503
Non-Guarantor Subsidiaries
Cash flows from operating activities
Net income (loss)	(93)		(67)		(268)	(273)
Adjustments to reconcile net income (loss) to net cash provided by operating activities					268	273
Cash
Beginning of period				$ 20	20	20
End of period	$ 20		$ 20		$ 20	$ 20