INVESTMENT IN OIL AND GAS PROPERTIES - Guinea Concession - Revenue Split (Details) - Guinea Concession - bbl / d	12 Months Ended
	Jun. 30, 2017	Mar. 25, 2010
INVESTMENT IN OIL AND GAS PROPERTIES
Guinea's participating interest in development of discovery as percentage of costs, maximum (as a percent)	15.00%
Maximum
INVESTMENT IN OIL AND GAS PROPERTIES
Guinea's participating interest in development of discovery as percentage of costs, maximum (as a percent)		15.00%
From 0 to 2,000
INVESTMENT IN OIL AND GAS PROPERTIES
Guinea's share in revenue, after recovery cost of operations (as a percent)	25.00%
Contractor share in revenue, after recovery cost of operations (as a percent)	75.00%
From 0 to 2,000 | Minimum
INVESTMENT IN OIL AND GAS PROPERTIES
Daily production (in barrels per day)	0
From 0 to 2,000 | Maximum
INVESTMENT IN OIL AND GAS PROPERTIES
Daily production (in barrels per day)	2,000
From 2,001 to 5,000
INVESTMENT IN OIL AND GAS PROPERTIES
Guinea's share in revenue, after recovery cost of operations (as a percent)	30.00%
Contractor share in revenue, after recovery cost of operations (as a percent)	70.00%
From 2,001 to 5,000 | Minimum
INVESTMENT IN OIL AND GAS PROPERTIES
Daily production (in barrels per day)	2,001
From 2,001 to 5,000 | Maximum
INVESTMENT IN OIL AND GAS PROPERTIES
Daily production (in barrels per day)	5,000
From 5,001 to 100,000
INVESTMENT IN OIL AND GAS PROPERTIES
Guinea's share in revenue, after recovery cost of operations (as a percent)	41.00%
Contractor share in revenue, after recovery cost of operations (as a percent)	59.00%
From 5,001 to 100,000 | Minimum
INVESTMENT IN OIL AND GAS PROPERTIES
Daily production (in barrels per day)	5,001
From 5,001 to 100,000 | Maximum
INVESTMENT IN OIL AND GAS PROPERTIES
Daily production (in barrels per day)	100,000
Over 100,001
INVESTMENT IN OIL AND GAS PROPERTIES
Guinea's share in revenue, after recovery cost of operations (as a percent)	60.00%
Contractor share in revenue, after recovery cost of operations (as a percent)	40.00%
Over 100,001 | Minimum
INVESTMENT IN OIL AND GAS PROPERTIES
Daily production (in barrels per day)	100,001