SUPPLEMENTAL FINANCIAL DATA-OIL AND GAS PRODUCING ACTIVITIES (Standardized Measure of Discounted Future Cash Flows Relating to Proved Reserves) (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Discounted Future Net Cash Flows Relating to Proved Oil and Gas Reserves, Future Net Cash Flows
Future oil, natural gas, and natural gas liquids sales	$ 3,459,749	$ 6,929,652	$ 11,004,080
Future production costs	(1,165,344)	(2,166,681)	(2,892,047)
Future development costs	(676,684)	(1,444,144)	(2,027,516)
Future income taxes	(18,441)	(142,383)	(1,071,362)
Future net cash flows	1,599,280	3,176,444	5,013,155
10% annual discount for estimated timing of cash flows	(864,672)	(1,779,347)	(2,625,414)
Standardized measure of discounted future net cash flows	734,608	1,397,097	2,387,741
Increase (Decrease) in Standardized Measure of Discounted Future Net Cash Flow Relating to Proved Oil and Gas Reserves
Standardized measure of discounted future net cash flows relating to proved oil, natural gas, and NGL reserves, at beginning of year	1,397,097	2,387,741	2,170,446
Changes resulting from:
Sales of oil, natural gas, and NGL net of production costs		(448,614)	(550,013)
Net changes in prices and future production costs		(1,235,758)	118,714
Net changes in future development costs		(4,188)	(56,422)
Extensions, discoveries, and improved recovery		572,516	667,323
Development costs incurred during the period		140,111	231,270
Revisions of previous quantity estimates		(355,565)	(220,389)
Changes in production rates, timing, and other		(34,665)	(173,222)
Sales of reserves in place		(213,683)	(107,742)
Purchases of reserves in place		0	0
Accretion of discount on reserves at beginning of year		263,316	258,303
Net change in income taxes		325,886	49,473
Total change for year		(990,644)	217,295
Standardized measure of discounted future net cash flows relating to proved oil, natural gas, and NGL reserves, at end of year		1,397,097	2,387,741
Discount rate applied to cash flow amounts in computation of standardized measure of discounted future net cash flows (as a percent)	10.00%
United States
Discounted Future Net Cash Flows Relating to Proved Oil and Gas Reserves, Future Net Cash Flows
Future oil, natural gas, and natural gas liquids sales	3,459,749	6,929,652	10,427,716
Future production costs	(1,165,344)	(2,166,681)	(2,692,993)
Future development costs	(676,684)	(1,444,144)	(2,008,824)
Future income taxes	(18,441)	(142,383)	(940,526)
Future net cash flows	1,599,280	3,176,444	4,785,373
10% annual discount for estimated timing of cash flows	(864,672)	(1,779,347)	(2,499,631)
Standardized measure of discounted future net cash flows	734,608	1,397,097	2,285,742
Increase (Decrease) in Standardized Measure of Discounted Future Net Cash Flow Relating to Proved Oil and Gas Reserves
Standardized measure of discounted future net cash flows relating to proved oil, natural gas, and NGL reserves, at beginning of year	1,397,097	2,285,742	1,964,920
Changes resulting from:
Sales of oil, natural gas, and NGL net of production costs	(337,914)	(448,614)	(550,013)
Net changes in prices and future production costs	222,516	(1,226,494)	272,027
Net changes in future development costs	50,568	(4,188)	(55,725)
Extensions, discoveries, and improved recovery	295,585	572,516	667,323
Development costs incurred during the period	128,482	140,111	231,270
Revisions of previous quantity estimates	(114,712)	(203,987)	(220,389)
Changes in production rates, timing, and other	19,321	(34,665)	(132,714)
Sales of reserves in place	(1,099,372)	(213,683)	(107,742)
Purchases of reserves in place	0	0	0
Accretion of discount on reserves at beginning of year	143,432	259,393	226,354
Net change in income taxes	29,605	270,966	(9,569)
Total change for year	(662,489)	(888,645)	320,822
Standardized measure of discounted future net cash flows relating to proved oil, natural gas, and NGL reserves, at end of year	734,608	1,397,097	2,285,742
Italy
Discounted Future Net Cash Flows Relating to Proved Oil and Gas Reserves, Future Net Cash Flows
Future oil, natural gas, and natural gas liquids sales	0	0	576,364
Future production costs	0	0	(199,054)
Future development costs	0	0	(18,692)
Future income taxes	0	0	(130,836)
Future net cash flows	0	0	227,782
10% annual discount for estimated timing of cash flows	0	0	(125,783)
Standardized measure of discounted future net cash flows	0	0	101,999
Increase (Decrease) in Standardized Measure of Discounted Future Net Cash Flow Relating to Proved Oil and Gas Reserves
Standardized measure of discounted future net cash flows relating to proved oil, natural gas, and NGL reserves, at beginning of year	0	101,999	205,526
Changes resulting from:
Sales of oil, natural gas, and NGL net of production costs		0	0
Net changes in prices and future production costs		(9,264)	(153,313)
Net changes in future development costs		0	(697)
Extensions, discoveries, and improved recovery		0	0
Development costs incurred during the period		0	0
Revisions of previous quantity estimates		(151,578)	0
Changes in production rates, timing, and other		0	(40,508)
Sales of reserves in place		0	0
Purchases of reserves in place		0	0
Accretion of discount on reserves at beginning of year		3,923	31,949
Net change in income taxes		54,920	59,042
Total change for year		(101,999)	(103,527)
Standardized measure of discounted future net cash flows relating to proved oil, natural gas, and NGL reserves, at end of year		$ 0	$ 101,999
Henry Hub
Changes resulting from:
Average price used in calculating standardized measure of discounted future net cash flows proved reserves (in dollars per MMBtu/barrel)	3.67	2.76	4.12
West Texas Intermediate
Changes resulting from:
Average price used in calculating standardized measure of discounted future net cash flows proved reserves (in dollars per MMBtu/barrel)	97.33	94.79	96.08