Supplemental Condensed Consolidating Financial Information (Supplemental Condensed Consolidating Statement of Cash Flows) (Details) - USD ($) $ in Thousands	1 Months Ended	3 Months Ended		5 Months Ended	6 Months Ended			9 Months Ended		12 Months Ended
	Jun. 30, 2014	Sep. 30, 2014	Sep. 30, 2013	Jun. 03, 2014	Dec. 31, 2014	Dec. 31, 2013	Jun. 30, 2013	Mar. 31, 2015	Mar. 31, 2014	Jun. 30, 2015	Jun. 30, 2014	Dec. 31, 2013	Jun. 30, 2013	Dec. 31, 2012
Net cash provided by operating activities	$ 22,209			$ 105,122			$ 192,476
Cash flows provided by (used in) investing activities:
Net cash used in investing activities	(200,929)			(258,714)			(154,969)
Cash flows provided by (used in) financing activities:
Net cash provided by (used in) financing activities	(15,729)			344,830			(35,143)
Net increase in cash and cash equivalents	(194,449)			191,238			2,364
Cash and cash equivalents at beginning of period	200,050	$ 5,601	$ 3,885	8,812	$ 5,601	$ 3,885	1,521	$ 5,601	$ 3,885	$ 5,601	$ 3,885	$ 1,521
Cash and cash equivalents at end of period	5,601			200,050		8,812	3,885				5,601	8,812	$ 3,885	$ 1,521
Successor Company [Member]
Net cash provided by operating activities	22,209	62,848			98,901			90,344		126,007
Cash flows provided by (used in) investing activities:
Property acquisitions	(141,886)	(260)			(350)			(350)		(350)
Capital expenditures	(58,976)	(111,136)			(239,090)			(271,496)		(298,849)
Other property and equipment additions	(67)	(40)			(58)			(58)		(58)
Proceeds from sale of assets										5,000
Net cash used in investing activities	(200,929)	(111,436)			(239,498)			(271,904)		(294,257)
Cash flows provided by (used in) financing activities:
Proceeds from indebtedness	475,000
Repayments of indebtedness	(475,000)							(325,000)		(325,000)
Proceeds from intercompany promissory note								325,000		325,000
Payments on put financing										(1,751)
Advances to EGC	(15,729)	43,010			135,480			177,832		165,768
Deferred financing costs								(1,089)		(1,151)
Other								(689)
Net cash provided by (used in) financing activities	(15,729)	43,010			135,480			176,054		162,866
Net increase in cash and cash equivalents	(194,449)	(5,578)			(5,117)			(5,506)		(5,384)	5,601
Cash and cash equivalents at beginning of period	200,050	5,601			5,601			5,601		5,601
Cash and cash equivalents at end of period	5,601	23		200,050	484			95		217	5,601
Successor Company [Member] | Parent Company [Member]
Net cash provided by operating activities	22,163	58,897			93,232			83,979		120,340
Cash flows provided by (used in) investing activities:
Property acquisitions	(141,886)	(260)			(350)			(350)		(350)
Capital expenditures	(58,930)	(107,185)			(233,421)			(265,131)		(293,182)
Other property and equipment additions	(67)	(40)			(58)			(58)		(58)
Proceeds from sale of assets										5,000
Net cash used in investing activities	(200,883)	(107,485)			(233,829)			(265,539)		(288,590)
Cash flows provided by (used in) financing activities:
Proceeds from indebtedness	475,000
Repayments of indebtedness	(475,000)							(325,000)		(325,000)
Proceeds from intercompany promissory note								325,000		325,000
Payments on put financing										(1,751)
Advances to EGC	(15,729)	43,010			135,480			177,832		165,768
Deferred financing costs								(1,089)		(1,151)
Other								(689)
Net cash provided by (used in) financing activities	(15,729)	43,010			135,480			176,054		162,866
Net increase in cash and cash equivalents	(194,449)	(5,578)			(5,117)			(5,506)		(5,384)
Cash and cash equivalents at beginning of period	200,050	5,601			5,601			5,601		5,601
Cash and cash equivalents at end of period	5,601	23		200,050	484			95		217	$ 5,601
Successor Company [Member] | Guarantor Subsidiaries [Member]
Net cash provided by operating activities	46	3,951			$ 5,669			6,365		5,667
Cash flows provided by (used in) investing activities:
Property acquisitions
Capital expenditures	(46)	(3,951)			$ (5,669)			(6,365)		(5,667)
Other property and equipment additions
Net cash used in investing activities	$ (46)	$ (3,951)			$ (5,669)			$ (6,365)		$ (5,667)
Cash flows provided by (used in) financing activities:
Advances to EGC
Net cash provided by (used in) financing activities
Net increase in cash and cash equivalents
Cash and cash equivalents at beginning of period
Cash and cash equivalents at end of period
Successor Company [Member] | Reclassifications & Eliminations [Member]
Net cash provided by operating activities
Cash flows provided by (used in) investing activities:
Property acquisitions
Capital expenditures
Other property and equipment additions
Proceeds from sale of assets
Net cash used in investing activities
Cash flows provided by (used in) financing activities:
Repayments of indebtedness
Proceeds from intercompany promissory note
Payments on put financing
Advances to EGC
Deferred financing costs
Other
Net cash provided by (used in) financing activities
Net increase in cash and cash equivalents
Cash and cash equivalents at beginning of period
Cash and cash equivalents at end of period
Predecessor Company [Member]
Net cash provided by operating activities			116,685	105,122		195,083			258,023			387,559		213,871
Cash flows provided by (used in) investing activities:
Decrease in restricted cash			51,757			51,757			51,757
Property acquisitions			(24,897)	(60,495)		(25,478)			(83,412)			(27,560)		(578,372)
Deposit for Nexen Acquisition						(7,040)			(7,040)			(7,040)
Capital expenditures			(100,021)	(197,968)		(169,936)			(268,905)			(322,040)		(184,850)
Other property and equipment additions			(254)	(251)		(753)			(984)			(2,016)		(1,743)
Proceeds from sale of assets						80			80			52,317
Net cash used in investing activities			(73,415)	(258,714)		(151,370)			(308,504)			(306,339)		(764,965)
Cash flows provided by (used in) financing activities:
Proceeds from indebtedness				345,000										509,313
Repayments of indebtedness			(40,000)			(35,000)			55,000			(65,000)		(20,000)
Deferred financing costs			(32)	(170)		(36)			(206)			(674)		(8,469)
Purchase of shares into treasury			(4,544)			(4,544)			(4,544)			(9,640)		(8,798)
Exercise of stock options			360			794			794			1,385		441
Net cash provided by (used in) financing activities			(44,216)	344,830		(38,786)			51,044			(73,929)		472,487
Net increase in cash and cash equivalents			(946)	191,238		4,927			563			7,291	3,885	(78,607)
Cash and cash equivalents at beginning of period	$ 200,050		3,885	8,812		3,885	1,521		3,885		$ 3,885	1,521		80,128
Cash and cash equivalents at end of period			2,939	200,050		8,812	3,885		4,448			8,812	3,885	1,521
Predecessor Company [Member] | Parent Company [Member]
Net cash provided by operating activities			99,497	102,307		173,834			235,046			356,597		190,851
Cash flows provided by (used in) investing activities:
Decrease in restricted cash			51,757			51,757			51,757
Property acquisitions			(24,897)	(57,680)		(25,478)			(83,412)			(27,560)		(575,372)
Deposit for Nexen Acquisition						(7,040)			(7,040)			(7,040)
Capital expenditures			(82,833)	(197,968)		(148,687)			(245,928)			(284,073)		(165,308)
Other property and equipment additions			(254)	(251)		(753)			(984)			(2,016)		(1,265)
Proceeds from sale of assets						80			80			45,312
Net cash used in investing activities			(56,227)	(255,899)		(130,121)			(285,527)			(275,377)		(741,945)
Cash flows provided by (used in) financing activities:
Proceeds from indebtedness				345,000										509,313
Repayments of indebtedness			(40,000)			(35,000)			55,000			(65,000)		(20,000)
Deferred financing costs			(32)	(170)		(36)			(206)			(674)		(8,469)
Purchase of shares into treasury			(4,544)			(4,544)			(4,544)			(9,640)		(8,798)
Exercise of stock options			360			794			794			1,385		441
Net cash provided by (used in) financing activities			(44,216)	344,830		(38,786)			51,044			(73,929)		472,487
Net increase in cash and cash equivalents			(946)	191,238		4,927			563			7,291		(78,607)
Cash and cash equivalents at beginning of period	$ 200,050		3,885	8,812		3,885	1,521		3,885		$ 3,885	1,521		80,128
Cash and cash equivalents at end of period			2,939	200,050		8,812	$ 3,885		4,448			8,812	$ 3,885	1,521
Predecessor Company [Member] | Guarantor Subsidiaries [Member]
Net cash provided by operating activities			17,188	2,815		21,249			22,977			30,962		23,020
Cash flows provided by (used in) investing activities:
Property acquisitions				(2,815)										(3,000)
Capital expenditures			(17,188)			(21,249)			(22,977)			(37,967)		(19,542)
Other property and equipment additions														(478)
Proceeds from sale of assets												7,005
Net cash used in investing activities			$ (17,188)	$ (2,815)		$ (21,249)			$ (22,977)			$ (30,962)		$ (23,020)
Predecessor Company [Member] | Reclassifications & Eliminations [Member]
Net cash provided by operating activities
Cash flows provided by (used in) investing activities:
Decrease in restricted cash
Property acquisitions
Deposit for Nexen Acquisition
Capital expenditures
Other property and equipment additions
Proceeds from sale of assets
Net cash used in investing activities
Cash flows provided by (used in) financing activities:
Repayments of indebtedness
Deferred financing costs
Purchase of shares into treasury
Exercise of stock options
Net cash provided by (used in) financing activities
Net increase in cash and cash equivalents
Cash and cash equivalents at beginning of period
Cash and cash equivalents at end of period