Acquisitions (Details 5) (USD $)	3 Months Ended								6 Months Ended	12 Months Ended
	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Mar. 31, 2013 item	Mar. 31, 2012
Acquisitions
Number of business combination agreements										2
Liabilities assumed in the form of non-compete agreements	$ 5,000,000									$ 5,000,000
Consideration paid for acquisition
Cash paid to acquire ownership interests	14,000,000									14,000,000
Cost of sales contributed by retail combinations	1,481,890,000	1,204,545,000	1,053,690,000	298,985,000	389,806,000	439,790,000	201,454,000	185,973,000	583,032,000	4,039,110,000	1,217,023,000
Vehicles | Minimum
Estimated fair value of the assets acquired and liabilities assumed
Useful life of property, plant and equipment										5 years	5 years
Vehicles | Maximum
Estimated fair value of the assets acquired and liabilities assumed
Useful life of property, plant and equipment										10 years	10 years
Buildings | Minimum
Estimated fair value of the assets acquired and liabilities assumed
Useful life of property, plant and equipment											5 years
Common units
Acquisitions
Number of common units issued to acquire ownership interests (in shares)										24,250,258	14,432,031
Retail and distillate operations acquisitions
Acquisitions
Number of business combination agreements										6
Liabilities assumed in the form of non-compete agreements	6,600,000									6,600,000
General and administrative expense	300,000									300,000
Estimated fair value of the assets acquired and liabilities assumed
Accounts receivable	8,715,000									8,715,000
Inventory	5,155,000									5,155,000
Other current assets	1,228,000									1,228,000
Goodwill	21,983,000									21,983,000
Other noncurrent assets	784,000									784,000
Long-term debt	(6,594,000)									(6,594,000)
Other assumed liabilities	(12,511,000)									(12,511,000)
Consideration paid, net of cash acquired	90,266,000									90,266,000
Consideration paid for acquisition
Cash paid to acquire ownership interests	71,392,000									71,392,000
Total consideration paid	90,266,000									90,266,000
Revenues										124,300,000
Cost of sales contributed by retail combinations										86,600,000
Retail and distillate operations acquisitions | Trade names
Estimated fair value of the assets acquired and liabilities assumed
Intangible assets	2,924,000									2,924,000
Retail and distillate operations acquisitions | Customer relationships
Estimated fair value of the assets acquired and liabilities assumed
Intangible assets	16,890,000									16,890,000
Retail and distillate operations acquisitions | Customer relationships | Minimum
Estimated fair value of the assets acquired and liabilities assumed
Useful life of intangible assets										10 years
Retail and distillate operations acquisitions | Customer relationships | Maximum
Estimated fair value of the assets acquired and liabilities assumed
Useful life of intangible assets										15 years
Retail and distillate operations acquisitions | Non-compete agreements
Estimated fair value of the assets acquired and liabilities assumed
Intangible assets	1,387,000									1,387,000
Useful life of intangible assets										5 years
Retail and distillate operations acquisitions | Land
Estimated fair value of the assets acquired and liabilities assumed
Property, plant and equipment	1,945,000									1,945,000
Retail and distillate operations acquisitions | Tanks and other retail propane equipment
Estimated fair value of the assets acquired and liabilities assumed
Property, plant and equipment	28,763,000									28,763,000
Retail and distillate operations acquisitions | Tanks and other retail propane equipment | Minimum
Estimated fair value of the assets acquired and liabilities assumed
Useful life of property, plant and equipment										5 years
Retail and distillate operations acquisitions | Tanks and other retail propane equipment | Maximum
Estimated fair value of the assets acquired and liabilities assumed
Useful life of property, plant and equipment										20 years
Retail and distillate operations acquisitions | Vehicles
Estimated fair value of the assets acquired and liabilities assumed
Property, plant and equipment	11,344,000									11,344,000
Useful life of property, plant and equipment										5 years
Retail and distillate operations acquisitions | Buildings
Estimated fair value of the assets acquired and liabilities assumed
Property, plant and equipment	7,052,000									7,052,000
Useful life of property, plant and equipment										30 years
Retail and distillate operations acquisitions | Other
Estimated fair value of the assets acquired and liabilities assumed
Property, plant and equipment	1,201,000									1,201,000
Retail and distillate operations acquisitions | Common units
Acquisitions
Number of common units issued to acquire ownership interests (in shares)										850,676	850,676
Consideration paid for acquisition
Value of common units issued to acquire ownership interests	$ 18,900,000	$ 18,874,000								$ 18,900,000