OIL AND GAS RESERVE DATA (UNAUDITED) (Details 2) (USD $)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Standardized Measure of Discounted Future Net Cash Flows Relating to Proved Oil and Gas Reserves
Future cash inflows	$ 1,928,019,000	$ 1,836,212,000	$ 1,708,079,000
Future production costs and taxes	(688,056,000)	(574,959,000)	(514,968,000)
Future development costs	(314,091,000)	(303,062,000)	(254,982,000)
Future income tax expenses	(82,576,000)	(105,078,000)	(108,977,000)
Net future cash flows	843,296,000	853,113,000	829,152,000
Discounted at 10% for estimated timing of cash flows	(368,295,000)	(393,233,000)	(343,146,000)
Standardized measure of discounted future net cash flows	475,001,000	459,880,000	486,006,000
Asset retirement obligations	64,400,000	79,900,000	66,300,000
Changes in Standardized Measure of Discounted Future Net Cash Flows Related to Proved Oil and Gas Reserves
Sales, net of production costs and taxes	(91,146,000)	(88,725,000)	(72,734,000)
Discoveries and extensions	52,189,000	108,438,000	152,973,000
Purchases of reserves in place	2,823,000	4,966,000
Changes in prices and production costs	(109,000)	(17,286,000)	196,010,000
Revisions of quantity estimates	22,911,000	(39,172,000)	56,710,000
Development costs incurred	(39,233,000)	36,539,000	30,892,000
Net changes in development costs	(10,502,000)	(90,392,000)	(149,662,000)
Interest factor-accretion of discount	49,491,000	48,601,000	28,763,000
Net change in income taxes	6,328,000	5,037,000	(40,070,000)
Changes in production rates (timing) and other	22,369,000	5,868,000	(4,504,000)
Net (decrease) increase	15,121,000	(26,126,000)	198,378,000
Balance at beginning of year	459,880,000	486,006,000	287,628,000
Balance at end of year	475,001,000	459,880,000	486,006,000
Oil prices weighted by production over lives of proved reserves	97.33	104.27	104.75
Gas prices weighted by production over lives of proved reserves	3.43	2.51	3.21
Future cash flows estimated to be spent to develop proved undeveloped properties	$ 249,700,000