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Amount of accumulated interest costs capitalized as part of property, plant and equipment cost basis.

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The charge against earnings in the period for known or estimated future costs arising from requirements to perform environmental remediation activities.

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Useful life of finite-lived intangible assets, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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Major Accounting Policies (Narrative) (Details) - USD ($)	3 Months Ended								12 Months Ended
	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2016
Accounting Policies [Abstract]
Environmental expenditures									$ 12,800,000	$ 11,400,000	$ 12,200,000
Allowance for doubtful accounts	$ 91,300,000				$ 93,500,000				91,300,000	93,500,000
Provision for doubtful accounts									24,000,000.0	45,800,000	21,800,000
Capitalized interest	19,500,000				19,000,000.0				19,500,000	19,000,000.0	32,700,000
Asset retirement obligations	190,400,000				144,700,000				190,400,000	144,700,000	119,900,000
Finite-Lived Intangible Assets [Line Items]
Finite-lived intangible assets, residual value	0								0
Change in Accounting Estimate [Line Items]
Operating income	$ 533,700,000	$ 515,800,000	$ 455,400,000	$ 460,700,000	$ 457,400,000	$ 258,700,000	$ 395,600,000	$ 328,300,000	$ 1,965,600,000	1,440,000,000.0	1,535,100,000
Software and Software Development Costs \| Minimum
Property, Plant and Equipment [Line Items]
Property and equipment, useful life									3 years
Software and Software Development Costs \| Maximum
Property, Plant and Equipment [Line Items]
Property and equipment, useful life									5 years
Customer relationships \| Minimum
Finite-Lived Intangible Assets [Line Items]
Finite-lived intangible assets, useful life									5 years
Customer relationships \| Maximum
Finite-Lived Intangible Assets [Line Items]
Finite-lived intangible assets, useful life									25 years
Patents and technology \| Minimum
Finite-Lived Intangible Assets [Line Items]
Finite-lived intangible assets, useful life									5 years
Patents and technology \| Maximum
Finite-Lived Intangible Assets [Line Items]
Finite-lived intangible assets, useful life									15 years
Land Use Rights
Finite-Lived Intangible Assets [Line Items]
Finite-lived intangible assets, useful life									50 years
Contracts accounted for under percentage of completion
Change in Accounting Estimate [Line Items]
Operating income									$ 38,000,000	$ 27,000,000	$ 20,000,000