RELATED PARTY TRANSACTIONS (Details) (EnerVest, Ltd. [Member], USD $) In Millions, unless otherwise specified	3 Months Ended	9 Months Ended
Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
EnerVest, Ltd. [Member]
Related Party Transaction [Line Items]
Administrative fees paid to related party	$ 2.5	$ 3.2	$ 7.5	$ 9.8
Direct expenses incurred and reimbursed to related party	$ 4.2	$ 4.0	$ 12.0	$ 12.1

Amount of selling, general and administrative expenses resulting from transactions, excluding transactions that are eliminated in consolidated or combined financial statements, with related party.

No definition available.

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Balance Type:	debit
Period Type:	duration