Segment Information (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Mar. 31, 2012	Mar. 31, 2011	Mar. 31, 2012	Mar. 31, 2011	Sep. 30, 2011
Segment information
Revenues	$ 2,427.5	$ 2,181.0	$ 4,116.3	$ 3,946.6
Cost of sales	1,526.6	1,423.9	2,628.4	2,586.5
Segment profit:
Operating income (loss)	380.8	357.0	569.1	609.3
Loss from equity investees		(0.4)	(0.1)	(0.6)
Loss on extinguishment of debt	(13.4)	(18.8)	(13.4)	(18.8)
Interest expense	(65.3)	(34.3)	(101.3)	(67.6)
Income (loss) before income taxes	302.1	303.5	454.3	522.3
Noncontrolling interests' net income	93.6	66.2	116.7	108.1
Depreciation and amortization	82.8	55.5	143.1	110.8
Capital expenditures	65.3	65.3	154.0	167.6
Total assets (at period end)	10,129.4	6,894.4	10,129.4	6,894.4	6,663.3
Bank loans (at period end)	190.2	222.1	190.2	222.1	138.7
Goodwill	2,795.2	1,588.4	2,795.2	1,588.4	1,562.2
Eliminations [Member]
Segment information
Revenues	(43.6)	(92.8)	(96.9)	(132.9)
Cost of sales	(42.4)	(91.9)	(94.7)	(131.2)
Segment profit:
Operating income (loss)		0.1		0.2
Income (loss) before income taxes		0.1		0.2
Total assets (at period end)	(84.4)	(89.3)	(84.4)	(89.3)
AmeriGas Propane [Member]
Segment information
Revenues	1,155.6	906.8	1,839.4	1,607.0
Cost of sales	670.0	564.8	1,113.8	1,000.1
Segment profit:
Operating income (loss)	195.0	154.6	255.1	246.2
Loss on extinguishment of debt	(13.4)	(18.8)	(13.4)	(18.8)
Interest expense	(45.1)	(16.3)	(61.6)	(31.7)
Income (loss) before income taxes	136.5	119.5	180.1	195.7
Partnership EBITDA	224.5	157.5	308.2	270.8
Noncontrolling interests' net income	93.2	65.8	116.2	107.3
Depreciation and amortization	44.8	23.2	69.0	45.9
Capital expenditures	23.5	23.5	45.1	40.6
Total assets (at period end)	4,823.8	1,908.7	4,823.8	1,908.7
Bank loans (at period end)	50.9	194.0	50.9	194.0
Goodwill	1,881.3	693.9	1,881.3	693.9
Gas Utility [Member]
Segment information
Revenues	319.5	452.5	574.5	773.6
Cost of sales	177.5	288.6	319.2	483.5
Segment profit:
Operating income (loss)	85.0	100.9	146.2	176.0
Interest expense	(10.1)	(10.2)	(20.2)	(20.3)
Income (loss) before income taxes	74.9	90.7	126.0	155.7
Depreciation and amortization	12.2	12.3	24.3	24.5
Capital expenditures	25.7	25.7	47.5	33.6
Total assets (at period end)	2,038.5	2,045.2	2,038.5	2,045.2
Goodwill	182.1	180.1	182.1	180.1
Electric Utility [Member]
Segment information
Revenues	25.9	31.7	51.1	60.6
Cost of sales	15.3	20.2	30.5	38.8
Segment profit:
Operating income (loss)	3.4	3.0	6.6	6.6
Interest expense	(0.6)	(0.6)	(1.1)	(1.1)
Income (loss) before income taxes	2.8	2.4	5.5	5.5
Depreciation and amortization	1.0	1.0	1.9	2.0
Capital expenditures	1.3	1.3	2.3	4.1
Total assets (at period end)	155.4	158.3	155.4	158.3
Midstream Marketing [Member]
Segment information
Revenues	269.0	360.3	507.8	639.9
Cost of sales	221.6	305.4	420.4	545.5
Segment profit:
Operating income (loss)	30.6	40.8	54.5	68.3
Interest expense	(1.3)	(0.7)	(2.4)	(1.4)
Income (loss) before income taxes	29.3	40.1	52.1	66.9
Depreciation and amortization	3.0	1.9	5.8	3.6
Capital expenditures	5.9	5.9	34.0	62.8
Total assets (at period end)	643.1	574.5	643.1	574.5
Bank loans (at period end)	112.0		112.0
Goodwill	2.8	2.8	2.8	2.8
International Propane, Antargaz [Member]
Segment information
Revenues	445.3	392.7	746.9	728.7
Cost of sales	288.6	244.1	464.3	458.7
Segment profit:
Operating income (loss)	60.2	60.5	97.5	112.4
Loss from equity investees		(0.4)	(0.1)	(0.6)
Interest expense	(6.9)	(5.9)	(13.4)	(11.4)
Income (loss) before income taxes	53.3	54.2	84.0	100.4
Noncontrolling interests' net income	0.4	0.4	0.5	0.8
Depreciation and amortization	15.0	12.6	29.1	24.9
Capital expenditures	4.9	4.9	16.0	19.8
Total assets (at period end)	1,843.3	1,757.7	1,843.3	1,757.7
Goodwill	638.5	626.6	638.5	626.6
International Propane, Other [Member]
Segment information
Revenues	236.4	111.2	453.1	230.1
Cost of sales	185.2	82.1	353.3	169.2
Segment profit:
Operating income (loss)	10.0	1.3	14.4	3.4
Interest expense	(1.2)	(0.4)	(2.2)	(1.3)
Income (loss) before income taxes	8.8	0.9	12.2	2.1
Depreciation and amortization	6.4	4.1	11.9	9.0
Capital expenditures	3.9	3.9	8.7	6.0
Total assets (at period end)	548.4	380.8	548.4	380.8
Bank loans (at period end)	27.3	28.1	27.3	28.1
Goodwill	83.5	78.0	83.5	78.0
Corporate and Other [Member]
Segment information
Revenues	19.4	18.6	40.4	39.6
Cost of sales	10.8	10.6	21.6	21.9
Segment profit:
Operating income (loss)	(3.4)	(4.2)	(5.2)	(3.8)
Interest expense	(0.1)	(0.2)	(0.4)	(0.4)
Income (loss) before income taxes	(3.5)	(4.4)	(5.6)	(4.2)
Depreciation and amortization	0.4	0.4	1.1	0.9
Capital expenditures	0.1	0.1	0.4	0.7
Total assets (at period end)	161.3	158.5	161.3	158.5
Goodwill	$ 6.9	$ 7.0	$ 6.9	$ 7.0