Disclosures About Derivative Instruments and Hedging Activities (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2013	Sep. 30, 2013	Dec. 31, 2012
Balance sheet location and fair value of derivative assets and liabilities
Total Derivatives Assets	$ 2,130	$ 92	$ 4,971
Total Derivatives Liability	(3,344)	(6,726)	(39,664)
Derivative Assets	2,058	43	4,760
Derivative Liabilities	3,272	6,677	39,453
Interest rate contracts [Member] | Derivatives Designated as Hedging Instruments [Member] | Derivative financial instruments [Member]
Balance sheet location and fair value of derivative assets and liabilities
Derivative Assets	0		4,226
Interest rate contracts [Member] | Derivatives Designated as Hedging Instruments [Member] | Derivative financial instruments and other noncurrent liabilities [Member]
Balance sheet location and fair value of derivative assets and liabilities
Derivative Liabilities	0		30,412
Commodity contracts [Member] | Derivatives Subject to Utility Rate Regulation [Member] | Derivative financial instruments [Member]
Balance sheet location and fair value of derivative assets and liabilities
Derivative Assets	1,969		420
Commodity contracts [Member] | Derivatives Subject to Utility Rate Regulation [Member] | Derivative financial instruments and other noncurrent liabilities [Member]
Balance sheet location and fair value of derivative assets and liabilities
Derivative Liabilities	3,272		9,041
Commodity contracts [Member] | Derivatives Not Designated as Hedging Instruments [Member] | Derivative financial instruments [Member]
Balance sheet location and fair value of derivative assets and liabilities
Derivative Liabilities	0		0
Commodity contracts [Member] | Derivatives Not Designated as Hedging Instruments [Member] | Derivative financial instruments [Member]
Balance sheet location and fair value of derivative assets and liabilities
Derivative Assets	$ 89		$ 114