Derivatives and Hedging Disclosures and Fair Value Measurements (Details Textual) (USD $) In Millions, unless otherwise specified	Sep. 30, 2012 gal	Sep. 30, 2011 gal
Derivatives and hedging disclosures and fair value measurements (Additional Textual) [Abstract]
Aggregated cash posted as collateral in normal course of business	$ 0.5
Hedging losses secured under credit facility	5.7
Call Option [Member]
Derivatives and hedging disclosures and fair value measurements (Textual) [Abstract]
Derivative activity volume	2,800,000	5,500,000
Notional value	10.0	16.3
Fair value	0.10	1.20
Put Option [Member]
Derivatives and hedging disclosures and fair value measurements (Textual) [Abstract]
Derivative activity volume	6,800,000	1,700,000
Notional value	16.1	3.6
Fair value	0.10	0.09
Synthetic Calls [Member]
Derivatives and hedging disclosures and fair value measurements (Textual) [Abstract]
Derivative activity volume	75,200,000	80,000,000
Notional value	237.5	248.7
Fair value	3.70	(5.00)
Inventory [Member]
Derivatives and hedging disclosures and fair value measurements (Textual) [Abstract]
Derivative activity volume - physical inventory	3,300,000	3,100,000
Swap contract to buy heating oil [Member]
Derivatives and hedging disclosures and fair value measurements (Textual) [Abstract]
Derivative activity volume	7,100,000	2,300,000
Notional value	21.1	6.0
Fair value	0.80	0.30
Swap contracts to sell heating oil [Member]
Derivatives and hedging disclosures and fair value measurements (Textual) [Abstract]
Derivative activity volume	24,300,000	20,700,000
Notional value	75.3	62.2
Fair value	(0.30)	4.60
Swap contracts to sell heating oil [Member] | NYS ultra-low sulfur heating oil customers [Member]
Derivatives and hedging disclosures and fair value measurements (Textual) [Abstract]
Derivative activity volume	19,200,000
Future contract to buy heating oil [Member]
Derivatives and hedging disclosures and fair value measurements (Textual) [Abstract]
Derivative activity volume	22,600,000	2,700,000
Notional value	67.6	7.9
Fair value	1.70	(0.60)
Future contract to sell heating oil [Member]
Derivatives and hedging disclosures and fair value measurements (Textual) [Abstract]
Derivative activity volume	26,700,000	4,200,000
Notional value	80.3	12.0
Fair value	(1.90)	0.70
Swap contract to buy gasoline [Member]
Derivatives and hedging disclosures and fair value measurements (Textual) [Abstract]
Derivative activity volume	1,100,000	1,600,000
Notional value	2.8	4.5
Fair value	0.30	(0.40)
Swap contract to buy diesel [Member]
Derivatives and hedging disclosures and fair value measurements (Textual) [Abstract]
Derivative activity volume	1,100,000	1,500,000
Notional value	2.9	4.5
Fair value	0.30	(0.40)
Swap contract to buy diesel [Member] | NYS ultra-low sulfur heating oil customers [Member]
Derivatives and hedging disclosures and fair value measurements (Textual) [Abstract]
Derivative activity volume	19,200,000
Notional value	60.6
Fair value	$ (0.40)