Derivative Financial Instruments Derivative Financial Instruments - Oil and Gas Commodity Contracts (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Dec. 31, 2013	Dec. 31, 2013 Swap [Member] Natural Gas Commodity Contract [Member] MMBTU	Sep. 30, 2013 Swap [Member] Natural Gas Commodity Contract [Member] MMBTU	Dec. 31, 2013 Swap [Member] Natural Gas Commodity Contract [Member] Remainder of 2013 [Member] MMBTU	Dec. 31, 2013 Swap [Member] Oil Commodity Contract [Member] MBbls	Sep. 30, 2013 Swap [Member] Oil Commodity Contract [Member] MBbls	Dec. 31, 2013 Swap [Member] Oil Commodity Contract [Member] Remainder of 2013 [Member] MBbls	Dec. 31, 2013 Swap [Member] Oil Commodity Contract [Member] Year Four [Member]
Derivative [Line Items]
Document Period End Date	Dec. 31, 2013
Natural Gas, Volume		16,316,000.0	16,018,000.0	16,316,000.0
Weighted average strike price per Mmbtu/Bbl				4.15			91.87
December 31, 2013		$ (0.7)		$ (0.7)	$ (1.0)		$ (1.0)	$ (1.7)
Derivative, Commodity Contract, Oil Volume					272,000.0	375.0	272,000.0