RELATED PARTY TRANSACTIONS (Details) (EnerVest, Ltd. [Member], USD $) In Millions, unless otherwise specified	3 Months Ended
Mar. 31, 2013	Mar. 31, 2012
EnerVest, Ltd. [Member]
Related Party Transaction [Line Items]
Administrative fees paid to related party	$ 2.5	$ 3.3
Direct expenses incurred and reimbursed to related party	$ 4.3	$ 4.0

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.

Name:	us-gaap_RelatedPartyTransactionSellingGeneralAndAdministrativeExpensesFromTransactionsWithRelatedParty
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration