Financial Instruments Financial Instruments at Fair Value (Details) (USD $)	Sep. 30, 2014		Sep. 30, 2013
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative Asset, Current	$ 45,827,000		$ 11,966,000
Derivative Asset, Noncurrent	13,038,000		109,354,000
Derivative Liability, Current	1,730,000		1,543,000
Derivative Liability, Noncurrent	20,126,000		0
Derivative Assets (Liabilities), at Fair Value, Net	37,009,000		119,777,000
Derivative, Cash Collateral	25,800,000		24,800,000
Derivative Liability, Collateral, Right to Reclaim Cash, Offset	3,100,000		14,700,000
Derivative, Collateral, Right to Reclaim Cash	22,700,000		10,100,000
Regulated Distribution Segment [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative Asset, Current	23,102,000		1,837,000
Derivative Asset, Noncurrent	13,038,000		109,354,000
Derivative Liability, Current	1,730,000		1,543,000
Derivative Liability, Noncurrent	20,126,000		0
Derivative Assets (Liabilities), at Fair Value, Net	14,284,000		109,648,000
Derivative Liability, Collateral, Right to Reclaim Cash, Offset	0		0
Derivative, Collateral, Right to Reclaim Cash	0		0
Nonregulated Segment [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative Asset, Current	22,725,000	[1]	10,129,000	[2]
Derivative Asset, Noncurrent	0		0
Derivative Liability, Current	0	[1]	0	[2]
Derivative Liability, Noncurrent	0		0
Derivative Assets (Liabilities), at Fair Value, Net	22,725,000		10,129,000
Derivative Liability, Collateral, Right to Reclaim Cash, Offset	3,033,000		14,705,000
Derivative, Collateral, Right to Reclaim Cash	$ 22,725,000		$ 10,124,000

[1] Includes $25.8 million of cash held on deposit to collateralize certain financial instruments. Of this amount, $3.1 million was used to offset current and noncurent risk management liabilities under master netting arrangements and the remaining $22.7 million is classified as current risk management assets.

[2] Includes $24.8 million of cash held on deposit to collateralize certain financial instruments. Of this amount, $14.7 million was used to offset current and noncurrent risk management liabilities under master netting arrangements and the remaining $10.1 million is classified as current risk management assets.