OIL AND GAS RESERVE DATA (UNAUDITED) - Standardized Measure of Discounted Future Net Cash Flows (Detail 2) $ in Thousands	12 Months Ended
	Dec. 31, 2015 USD ($) $ / bbl $ / Mcf	Dec. 31, 2014 USD ($) $ / bbl $ / Mcf	Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)	Dec. 31, 2012 USD ($)
Standardized Measure of Discounted Future Net Cash Flows Relating to Proved Oil and Gas Reserves
Future cash inflows			$ 862,751	$ 2,510,062
Future production costs and taxes			(503,702)	(967,776)
Future development costs			(180,790)	(390,057)
Future income tax expenses				(140,458)
Net future cash flows			178,259	1,011,771
Discounted at 10% for estimated timing of cash flows			(82,236)	(456,704)
Standardized measure of discounted future net cash flows	$ 555,067	$ 555,067	$ 96,023	$ 555,067	$ 475,001
Asset retirement obligations	55,800	69,700
Changes in Standardized Measure of Discounted Future Net Cash Flows Related to Proved Oil and Gas Reserves
Sales, net of production costs and taxes	(34,176)	(97,028)
Discoveries and extensions	2,540	40,720
Purchases of reserves in place		206,334
Changes in prices and production costs	(342,650)	(84,548)
Revisions of quantity estimates	(202,716)	47,425
Development costs incurred	(12,869)	(92,983)
Net changes in development costs	131,919	(134,255)
Interest factor-accretion of discount	55,506	50,371
Net change in income taxes	(54,059)	(25,354)
Changes in production rates (timing) and other	(28,277)	(16,582)
Net (decrease) increase	(459,044)	80,066
Balance at beginning of year	555,067	555,067
Balance at end of year	$ 96,023	$ 555,067
Oil prices weighted by production over lives of proved reserves | $ / bbl	42.81	86.71
Gas prices weighted by production over lives of proved reserves | $ / Mcf	1.74	3.22
Future cash flows estimated to be spent to develop proved undeveloped properties	$ 124,900