SUPPLEMENTAL INFORMATION - NATURAL GAS AND CRUDE OIL PROPERTIES Principal Sources of Change in Standardized Measure of Discounted Future Net Cash Flows (Unuadited) (Details) - USD ($)		12 Months Ended
		Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Principal Sources of Change:
Sales of natural gas, NGL and crude oil production, net of production costs		$ (387,576,000)	$ (293,127,000)	$ (387,789,000)
Net changes in prices and production costs	[1]	(205,760,000)	(1,752,921,000)	129,213,000
Extensions, discoveries and improved recovery, less related costs		15,128,000	489,178,000	1,444,581,000
Sales of reserves		(3,745,000)	(463,000)	(402,595,000)
Purchases of reserves		487,636,000	374,000	238,000
Development costs incurred during the period		268,672,000	368,840,000	161,404,000
Revisions of previous quantity estimates		(320,286,000)	(1,286,462,000)	(654,318,000)
Changes in estimated income taxes		(13,630,000)	902,994,000	(221,874,000)
Net change in future development costs		391,145,000	112,958,000	46,499,000
Accretion of discount		133,747,000	345,007,000	270,389,000
Timing and other		(41,566,000)	(95,979,000)	138,554,000
Total		1,420,629,000	1,096,864,000	2,306,465,000	$ 1,782,163,000
Notes to Changes in SMOG [Abstract]
Weighted-Average price, net of production cost		$ 15.73	$ 17.30	$ 37.78

[1] Our weighted-average price, net of production costs per Boe, in our 2016 reserve report decreased to $15.73 as compared to $17.30 for 2015 and $37.78 for 2014