Supplemental Disclosures about Oil and Natural Gas Producing Properties (unaudited) - Estimated Quantities of Proved Oil and Natural Gas Reserves (Details)	12 Months Ended
	Jun. 30, 2017 Boe Mcf bbl		Jun. 30, 2016 Boe Mcf bbl		Jun. 30, 2015 Boe Mcf bbl		Jun. 30, 2014 Boe Mcf bbl
Estimated quantities of proved oil and natural gas reserves and changes in quantities of proved developed and undeveloped reserves
Balance at the beginning of the period (in BOE) | Boe	10,823,421		12,446,394		13,289,510
Revisions of previous estimates (in BOE) | Boe	3,390	[1]	(964,171)	[2]	(390,330)	[3]
Improved recovery, extensions and discoveries (in BOE) | Boe	0		0		0
Sales of minerals in place (in BOE) | Boe	0		0		0
Production (sales volumes) (in BOE) | Boe	(768,433)		(658,802)		(452,786)
Balance at the end of the period (in BOE) | Boe	10,058,378		10,823,421		12,446,394
Proved developed reserves (in BOE) | Boe	7,950,192		7,168,249		7,349,626		7,970,562
Proved undeveloped reserves (in BOE) | Boe	2,108,186		3,655,172		5,096,768		5,318,948
Crude Oil
Estimated quantities of proved oil and natural gas reserves and changes in quantities of proved developed and undeveloped reserves
Balance at the beginning of the period (in Bbls/Mcf)	8,588,550		10,011,976		10,526,344
Revisions of previous estimates (in Bbls/Mcf)	508,123	[1]	(765,385)	[2]	(64,074)	[3]
Improved recovery, extensions and discoveries (in Bbls/Mcf)	0		0		0
Sales of minerals in place (in Bbls/Mcf)	0		0		0
Production (sales volumes) (in Bbls/Mcf)	(724,523)		(658,041)		(450,294)
Balance at the end of the period (in Bbls/Mcf)	8,372,150		8,588,550		10,011,976
Estimated quantities of proved oil and natural gas reserves and changes in quantities of proved developed and undeveloped reserves
Proved developed reserves (in Bbls/Mcf)	6,617,389		7,168,249		7,347,231		7,858,224
Proved undeveloped reserves (in Bbls/Mcf)	1,754,761		1,420,301		2,664,745		2,668,120
Natural Gas Liquids
Estimated quantities of proved oil and natural gas reserves and changes in quantities of proved developed and undeveloped reserves
Balance at the beginning of the period (in Bbls/Mcf)	2,234,871		2,433,595		2,278,688
Revisions of previous estimates (in Bbls/Mcf)	(504,733)	[1]	(198,233)	[2]	156,195	[3]
Improved recovery, extensions and discoveries (in Bbls/Mcf)	0		0		0
Sales of minerals in place (in Bbls/Mcf)	0		0		0
Production (sales volumes) (in Bbls/Mcf)	(43,907)		(491)		(1,288)
Balance at the end of the period (in Bbls/Mcf)	1,686,231		2,234,871		2,433,595
Estimated quantities of proved oil and natural gas reserves and changes in quantities of proved developed and undeveloped reserves
Proved developed reserves (in Bbls/Mcf)	1,332,803		0		1,572		32,164
Proved undeveloped reserves (in Bbls/Mcf)	353,425		2,234,871		2,432,023		2,246,524
Natural Gas
Estimated quantities of proved oil and natural gas reserves and changes in quantities of proved developed and undeveloped reserves
Balance at the beginning of the period (in Bbls/Mcf) | Mcf	0		4,939		2,906,863
Revisions of previous estimates (in Bbls/Mcf) | Mcf	16	[1]	(3,319)	[2]	(2,894,703)	[3]
Improved recovery, extensions and discoveries (in Bbls/Mcf) | Mcf	0		0		0
Sales of minerals in place (in Bbls/Mcf) | Mcf	0		0		0
Production (sales volumes) (in Bbls/Mcf) | Mcf	(16)		(1,620)		(7,221)
Balance at the end of the period (in Bbls/Mcf) | Mcf	0		0		4,939
Estimated quantities of proved oil and natural gas reserves and changes in quantities of proved developed and undeveloped reserves
Proved developed reserves (in Bbls/Mcf) | Mcf	0		0		4,939		481,042
Proved undeveloped reserves (in Bbls/Mcf) | Mcf	0		0		0		2,425,821

[1] The positive crude oil revision resulted from better production performance during fiscal 2017 and the expectation of greater ultimate recoveries of oil from the Delhi field. The negative NGL revision results primarily from lower expectations for ultimate NGL recoveries from the plant based on production data after the plant commenced production.

[2] The negative revision results primarily from the removal of proved undeveloped reserves in the far eastern part of the Delhi field, referred to as Test Site 6, which were deemed uneconomic under the lower SEC price case utilized at the end of the period.

[3] The 2,894,703 revision for natural gas in fiscal 2015 primarily reflects a 2,246,524 MCF reduction for the Delhi field NGL plant together with a 452,786 MCF revision at the Giddings Field for a well that was lost due to mechanical issues. The NGL plant revision resulted from a decision to change in the plant design to use the methane production internally to reduce field operating costs rather than selling it into the market. The 156,195 BBL positive natural gas liquids revision primarily reflects 185,499 BBL positive revision for better recovery from the redesigned NGL plant, partly offset by a 29,304 BBL negative revision from the lost Giddings well.