SUPPLEMENTAL FINANCIAL DATA-OIL AND GAS PRODUCING ACTIVITIES (Capitalized Costs Relating to Oil and Gas Producing Activities) (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2013		Dec. 31, 2012
Capitalized costs relating to oil and gas producing activities
Costs related to proved properties	$ 9,213,668		$ 9,696,498
Costs related to unproved properties	53,645		277,798
Total costs proved and unproved properties	9,267,313		9,974,296
Less accumulated depletion	(8,460,589)	[1]	(8,237,186)	[1]
Net costs of oil and gas properties	$ 806,724		$ 1,737,110

[1] Includes inception-to-date ceiling test write-downs.