Derivative Financial Instruments Derivative Financial Instruments - Oil and Gas Commodity Contracts (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014 Swap [Member] Natural Gas Commodity Contract [Member] MMBTU	Sep. 30, 2013 Swap [Member] Natural Gas Commodity Contract [Member] MMBTU	Jun. 30, 2014 Swap [Member] Natural Gas Commodity Contract [Member] Remainder of 2014 [Member] MMBTU	Jun. 30, 2014 Swap [Member] Oil Commodity Contract [Member] MBbls	Sep. 30, 2013 Swap [Member] Oil Commodity Contract [Member] MBbls	Jun. 30, 2014 Swap [Member] Oil Commodity Contract [Member] Year Two [Member] MBbls	Jun. 30, 2014 Swap [Member] Oil Commodity Contract [Member] Remainder of 2014 [Member] MBbls	Jun. 30, 2014 Swap [Member] Energy Related Derivative [Member]
Derivative [Line Items]
Derivative, Percentage of Production Volume Covered by Derivative Financial Instruments	68.00%	77.00%	74.00%	70.00%
Document Period End Date			Jun. 30, 2014
Natural Gas, Volume					8,211,000.0	16,018,000.0	8,211,000.0
Weighted average strike price per Mmbtu/Bbl							4.15			94.98	91.87
June 30, 2014					$ (2.5)		$ (2.5)	$ (1.8)		$ (0.3)	$ (1.5)	$ (4.3)
Derivative, Commodity Contract, Oil Volume								323,000.0	375.0	186,000.0	137,000.0