DERIVATIVES - General (Details) - Crude Oil	Sep. 30, 2017 bbl / d $ / bbl bbl
Swaps | December 2017 Production
Derivatives
Maximum increase in volume for the period of crude oil counterparties swaps (in barrels per day) | bbl	5,000
Weighted-average strike price (in dollars per barrel)	55.03
Swaps | Q4 2017
Derivatives
Daily Volume (in Bbl) | bbl / d	30,000
Weighted-average price (in dollars per barrel)	55.00
Swaps | Q1 2018
Derivatives
Daily Volume (in Bbl) | bbl / d	29,000
Weighted-average price (in dollars per barrel)	60.00
Swaps | Q2 2018
Derivatives
Daily Volume (in Bbl) | bbl / d	29,000
Weighted-average price (in dollars per barrel)	60.00
Swaps | Q3 2018
Derivatives
Daily Volume (in Bbl) | bbl / d	19,000
Weighted-average price (in dollars per barrel)	60.13
Swaps | Q4 2018
Derivatives
Daily Volume (in Bbl) | bbl / d	19,000
Weighted-average price (in dollars per barrel)	60.13
Swaps | First half of 2018 production
Derivatives
Maximum increase in volume per quarter of crude oil counter-party swaps (in barrels) | bbl	19,000
Weighted-average price (in dollars per barrel)	60.00
Maximum increase in volume for the period of crude oil counterparties swaps (in barrels per day) | bbl	10,000
Weighted-average strike price (in dollars per barrel)	60.00
Swaps | Second half of 2018 production
Derivatives
Maximum increase in volume per quarter of crude oil counter-party swaps (in barrels) | bbl	19,000
Weighted-average price (in dollars per barrel)	60.13
Maximum increase in volume for the period of crude oil counterparties swaps (in barrels per day) | bbl	5,000
Weighted-average strike price (in dollars per barrel)	60.15
Purchased | Puts | Q4 2017
Derivatives
Daily Volume (in Bbl) | bbl / d	11,300
Weighted-average price (in dollars per barrel)	47.75
Purchased | Puts | Q1 2018
Derivatives
Daily Volume (in Bbl) | bbl / d	1,200
Weighted-average price (in dollars per barrel)	45.82
Purchased | Puts | Q2 2018
Derivatives
Daily Volume (in Bbl) | bbl / d	1,200
Weighted-average price (in dollars per barrel)	45.83
Purchased | Puts | Q3 2018
Derivatives
Daily Volume (in Bbl) | bbl / d	1,100
Weighted-average price (in dollars per barrel)	45.83
Purchased | Puts | Q4 2018
Derivatives
Daily Volume (in Bbl) | bbl / d	1,100
Weighted-average price (in dollars per barrel)	45.85
Purchased | Puts | FY 2019
Derivatives
Daily Volume (in Bbl) | bbl / d	1,000
Weighted-average price (in dollars per barrel)	45.84
Purchased | Puts | FY 2020
Derivatives
Daily Volume (in Bbl) | bbl / d	900
Weighted-average price (in dollars per barrel)	43.91
Sold | Calls | Q4 2017
Derivatives
Daily Volume (in Bbl) | bbl / d	6,300
Weighted-average price (in dollars per barrel)	57.80
Sold | Calls | Q1 2018
Derivatives
Daily Volume (in Bbl) | bbl / d	16,800
Weighted-average price (in dollars per barrel)	58.86
Sold | Calls | Q2 2018
Derivatives
Daily Volume (in Bbl) | bbl / d	16,200
Weighted-average price (in dollars per barrel)	58.92
Sold | Calls | Q3 2018
Derivatives
Daily Volume (in Bbl) | bbl / d	16,100
Weighted-average price (in dollars per barrel)	58.91
Sold | Calls | Q4 2018
Derivatives
Daily Volume (in Bbl) | bbl / d	16,100
Weighted-average price (in dollars per barrel)	58.91
Sold | Calls | FY 2019
Derivatives
Daily Volume (in Bbl) | bbl / d	1,000
Weighted-average price (in dollars per barrel)	60.00
Sold | Calls | FY 2020
Derivatives
Daily Volume (in Bbl) | bbl / d	900
Weighted-average price (in dollars per barrel)	60.00
Sold | Puts | Q1 2018
Derivatives
Daily Volume (in Bbl) | bbl / d	29,000
Weighted-average price (in dollars per barrel)	45.00
Sold | Puts | Q2 2018
Derivatives
Daily Volume (in Bbl) | bbl / d	29,000
Weighted-average price (in dollars per barrel)	45.00
Sold | Puts | Q3 2018
Derivatives
Daily Volume (in Bbl) | bbl / d	19,000
Weighted-average price (in dollars per barrel)	45.00
Sold | Puts | Q4 2018
Derivatives
Daily Volume (in Bbl) | bbl / d	19,000
Weighted-average price (in dollars per barrel)	45.00