DERIVATIVE INSTRUMENTS AND PRICE RISK MANAGEMENT - Classification of Outstanding Financial Instruments (Details) - USD ($)	Mar. 31, 2020	Dec. 31, 2019	Jun. 30, 2019
Offsetting Assets [Line Items]
Current Derivative Assets	$ 245,552,000	$ 5,628,000
Noncurrent Derivative Assets	94,329,000	8,554,000
Total derivative assets	345,503,000	36,233,000
Current liabilities	(130,000)	(11,298,000)
Noncurrent liabilities	(547,000)	(8,079,000)
Total derivative liabilities	(6,299,000)	(41,428,000)
Gross Amounts of Recognized Assets, Offsetting of Derivative Assets	345,503,000	36,233,000
Gross Amounts Offset in the Balance Sheet, Offsetting of Derivative Assets	(5,622,000)	(22,051,000)
Net Amounts of Assets Presented in the Balance Sheet, Offsetting of Derivative Assets	339,881,000	14,182,000
Gross Amounts of Recognized Assets, Offsetting of Derivative Liabilities	(6,299,000)	(41,428,000)
Gross Amounts Offset in the Balance Sheet, Offsetting of Derivative Liabilities	5,622,000	22,051,000
Net Amounts of Assets Presented in the Balance Sheet, Offsetting of Derivative Liabilities	(677,000)	(19,377,000)
Current Assets
Offsetting Assets [Line Items]
Gross Amounts of Recognized Assets, Offsetting of Derivative Assets	245,703,000	20,164,000
Gross Amounts Offset in the Balance Sheet, Offsetting of Derivative Assets	(151,000)	(14,536,000)
Net Amounts of Assets Presented in the Balance Sheet, Offsetting of Derivative Assets	245,552,000	5,628,000
Noncurrent Assets
Offsetting Assets [Line Items]
Gross Amounts of Recognized Assets, Offsetting of Derivative Assets	99,800,000	16,069,000
Gross Amounts Offset in the Balance Sheet, Offsetting of Derivative Assets	(5,471,000)	(7,515,000)
Net Amounts of Assets Presented in the Balance Sheet, Offsetting of Derivative Assets	94,329,000	8,554,000
Current Liabilities
Offsetting Assets [Line Items]
Gross Amounts of Recognized Assets, Offsetting of Derivative Liabilities	(281,000)	(25,834,000)
Gross Amounts Offset in the Balance Sheet, Offsetting of Derivative Liabilities	151,000	14,536,000
Net Amounts of Assets Presented in the Balance Sheet, Offsetting of Derivative Liabilities	(130,000)	(11,298,000)
Noncurrent Liabilities
Offsetting Assets [Line Items]
Gross Amounts of Recognized Assets, Offsetting of Derivative Liabilities	(6,019,000)	(15,594,000)
Gross Amounts Offset in the Balance Sheet, Offsetting of Derivative Liabilities	5,471,000	7,515,000
Net Amounts of Assets Presented in the Balance Sheet, Offsetting of Derivative Liabilities	(547,000)	(8,079,000)
Commodity Price Swap Contracts | Current Assets
Offsetting Assets [Line Items]
Current Derivative Assets	245,552,000	20,164,000
Commodity Price Swap Contracts | Noncurrent Assets
Offsetting Assets [Line Items]
Noncurrent Derivative Assets	99,800,000	16,069,000
Commodity Price Swap Contracts | Current Liabilities
Offsetting Assets [Line Items]
Current liabilities	0	(25,834,000)
Commodity Price Swap Contracts | Noncurrent Liabilities
Offsetting Assets [Line Items]
Noncurrent liabilities	0	(5,273,000)
Interest Rate Swap Contracts | Current Assets
Offsetting Assets [Line Items]
Current Derivative Assets	151,000	0
Interest Rate Swap Contracts | Noncurrent Assets
Offsetting Assets [Line Items]
Noncurrent Derivative Assets	1,000		$ 0
Interest Rate Swap Contracts | Current Liabilities
Offsetting Assets [Line Items]
Current liabilities	(281,000)		$ 0
Interest Rate Swap Contracts | Noncurrent Liabilities
Offsetting Assets [Line Items]
Noncurrent liabilities	(548,000)	0
Commodity Price Swaptions Contracts | Noncurrent Liabilities
Offsetting Assets [Line Items]
Noncurrent liabilities	$ (5,471,000)	$ (10,321,000)