Financial Instruments Financial Instruments at Fair Value (Details) - USD ($) $ in Thousands	Sep. 30, 2015		Sep. 30, 2014
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative Asset, Current	$ 9,232		$ 45,827
Derivative Asset, Noncurrent	368		13,038
Derivative Liability, Current	(9,568)		(1,730)
Derivative Liability, Noncurrent	(110,539)		(20,126)
Derivative Assets (Liabilities), at Fair Value, Net	(110,507)		37,009
Cash Held in Margin Accounts	43,500		25,800
Cash Held In Margin Accounts Used to Offset Risk Management Liabilities	34,600		3,100
Cash Held In Margin Accounts Classified Current Risk Management Asset	8,900		22,700
Regulated Distribution Segment [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative Asset, Current	378		23,102
Derivative Asset, Noncurrent	368		13,038
Derivative Liability, Current	(9,568)		(1,730)
Derivative Liability, Noncurrent	(110,539)		(20,126)
Derivative Assets (Liabilities), at Fair Value, Net	(119,361)		14,284
Cash Held In Margin Accounts Used to Offset Risk Management Liabilities	0		0
Cash Held In Margin Accounts Classified Current Risk Management Asset	0		0
Nonregulated Segment [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative Asset, Current	8,854	[1]	22,725	[2]
Derivative Asset, Noncurrent	0		0
Derivative Liability, Current	0	[1]	0	[2]
Derivative Liability, Noncurrent	0	[1]	0	[2]
Derivative Assets (Liabilities), at Fair Value, Net	8,854		22,725
Cash Held In Margin Accounts Used to Offset Risk Management Liabilities	34,620		3,033
Cash Held In Margin Accounts Classified Current Risk Management Asset	$ 8,854		$ 22,725

[1] Includes $43.5 million of cash held on deposit to collateralize certain financial instruments. Of this amount, $34.6 million was used to offset current and noncurent risk management liabilities under master netting arrangements and the remaining $8.9 million is classified as current risk management assets.

[2] 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 noncurrent risk management liabilities under master netting arrangements and the remaining $22.7 million is classified as current risk management assets.