Major Accounting Policies (Narratives) (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2014
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Allowance for credit losses - capital leases	$ 0.0				$ 0.0				$ 0.0	$ 0.0
Environmental expenditures									27.0	28.3	$ 35.1
Allowance for Doubtful Accounts	56.8				48.5				56.8	48.5
Provision for Doubtful Accounts									22.8	26.3	16.4
Capitalized interest	32.9				49.1				32.9	49.1	33.0
Asset retirement obligations	119.9				109.4				$ 119.9	109.4	94.0
Period for reallocation of purchase price									1 year
Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Asset, Residual Value	0.0								$ 0.0
Change in Accounting Estimate [Line Items]
Operating income (loss)	$ 547.0	$ 535.1	$ 513.3	$ 510.6	$ 474.3	$ 424.8	$ 376.9	$ 432.3	$ 2,106.0	$ 1,708.3	$ 1,339.1
Computer Software [Member] | Minimum [Member]
Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Asset, Useful Life									3 years
Computer Software [Member] | Maximum [Member]
Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Asset, Useful Life									10 years
Customer Relationships [Member] | Minimum [Member]
Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Asset, Useful Life									5 years
Customer Relationships [Member] | Maximum [Member]
Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Asset, Useful Life									25 years
Patents and Technology [Member] | Minimum [Member]
Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Asset, Useful Life									5 years
Patents and Technology [Member] | Maximum [Member]
Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Asset, Useful Life									20 years
Land Use Rights [Member]
Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Asset, Useful Life									50 years
Contracts accounted for under percentage of completion
Change in Accounting Estimate [Line Items]
Operating income (loss)									$ 20.0