Other Income Net (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended								12 Months Ended
	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2011
Other Cost and Expense Disclosure, Operating [Abstract]
Interest and interest-related income									$ 2.2	$ 2.4	$ 2.3
Antargaz Competition Authority matter									0	0	9.4
Utility non-tariff service income									2.8	2.7	6.4
Foreign currency hedge gain (loss)									(0.4)	0.5	(6.1)
Finance charges									21.4	18.8	15.1
Other-than-temporary impairment of an investment in a private equity partnership pre-tax loss	6.3								6.3	0	0
Other, net									13.1	15.4	18.4
Total other income, net	$ 8.3	$ 7.0	$ 7.5	$ 10.0	$ 10.8	$ 8.1	$ 12.8	$ 8.1	$ 32.8	$ 39.8	$ 45.5