SUPPLEMENTAL FINANCIAL DATA-OIL AND GAS PRODUCING ACTIVITIES (Cost Incurred in Oil and Gas Property Acquisition, Exploration, and Development Activities) (Details) (USD $)	12 Months Ended
	Dec. 31, 2013		Dec. 31, 2012		Dec. 31, 2011
Property acquisition costs:
Proved properties	$ 0		$ 0		$ 0
Unproved properties	7,117,000		64,123,000		204,484,000
Exploration costs	129,946,000		268,853,000		287,415,000
Development costs	213,127,000		399,123,000		417,835,000
Total costs incurred	350,190,000	[1]	732,099,000	[1]	909,734,000	[1]
Changes in estimated asset retirment obligations	8,600,000		6,100,000		3,100,000
United States
Property acquisition costs:
Proved properties	0		0		0
Unproved properties	7,117,000		64,123,000		204,484,000
Exploration costs	129,946,000		268,153,000		286,412,000
Development costs	213,127,000		398,941,000		417,469,000
Total costs incurred	350,190,000	[1]	731,217,000	[1]	908,365,000	[1]
Italy
Property acquisition costs:
Proved properties	0		0		0
Unproved properties	0		0		0
Exploration costs	0		700,000		1,003,000
Development costs	0		182,000		366,000
Total costs incurred	$ 0	[1]	$ 882,000	[1]	$ 1,369,000	[1]

[1] Includes amounts relating to changes in estimated asset retirement obligations of $8.6 million, $6.1 million, and $3.1 million recorded during the years ended December 31, 2013, 2012, and 2011, respectively.