Fair Value of Financial Instruments (Details 2) (USD $) In Thousands, unless otherwise specified	6 Months Ended	12 Months Ended		6 Months Ended		12 Months Ended									6 Months Ended	12 Months Ended		6 Months Ended
	Mar. 31, 2011	Mar. 31, 2013	Mar. 31, 2012	Sep. 30, 2010 NGL Supply	Mar. 31, 2011 Interest rate swaps	Mar. 31, 2013 Interest rate swaps	Mar. 31, 2012 Interest rate swaps	Mar. 31, 2013 Propane Swaps bbl	Mar. 31, 2012 Propane Swaps bbl	Mar. 31, 2013 Heating oil calls and futures bbl	Mar. 31, 2013 Crude swaps bbl	Mar. 31, 2013 Crude - butane spreads bbl	Mar. 31, 2013 Crude Forwards bbl	Mar. 31, 2013 Butane Forwards bbl	Mar. 31, 2011 Commodity contracts	Mar. 31, 2013 Commodity contracts	Mar. 31, 2012 Commodity contracts	Sep. 30, 2010 Commodity contracts NGL Supply
Derivative contract information
Total Notional Units (Barrels)								(282,000)	(460,000)	8,000	(91,000)	(1,116,000)	(144,000)	1,546,000
Fair Value of Net Assets (Liabilities)		$ (5,746)						$ 3,197	$ (36)	$ 79	$ 153	$ (7,651)	$ 1,033	$ (2,557)
Net cash collateral held		(1,360)
Net fair value of commodity derivatives on consolidated balance sheet		(7,106)
Net gains (losses) derivatives
Unrealized gain (loss)															1,357	(5,275)	(4,384)	(200)
Realized gain															111	899	10,351	426
Total	$ 1,692	$ (4,381)	$ 5,676	$ 226	$ 224	$ (5)	$ (291)