Supplementary Information For Oil And Gas Producing Activities (Capitalized Costs Relating To Oil And Gas Producing Activities) (Details) (USD $)	Sep. 30, 2014		Sep. 30, 2013
Supplementary Information For Oil And Gas Producing Activities Unaudited [Abstract]
Proved Properties	$ 3,941,143,000	[1]	$ 3,393,612,000	[1]
Unproved Properties	141,719,000		106,085,000
Capitalized Costs, Oil and Gas Producing Activities, Gross, Total	4,082,862,000		3,499,697,000
Less - Accumulated Depreciation, Depletion and Amortization	1,211,610,000		919,989,000
Capitalized Costs Oil And Gas Producing Activities Net	2,871,252,000		2,579,708,000
Asset retirement costs	$ 75,700,000		$ 80,600,000

[1] Includes asset retirement costs of $75.7 million and $80.6 million at September 30, 2014 and 2013, respectively.