Property, Plant and Equipment - Schedule of Property, Plant and Equipment (Details) - USD ($) $ in Millions	Dec. 31, 2019	Sep. 30, 2019
Property, plant and equipment at cost:
Property, plant and equipment, at cost	$ 17,811.5	$ 17,461.3
Less: accumulated depreciation, depletion and amortization	(6,530.4)	(6,271.8)
Property, plant and equipment, net	11,281.1	11,189.5
Land and Buildings [Member]
Property, plant and equipment at cost:
Property, plant and equipment, at cost	2,476.1	2,442.3
Machinery and Equipment [Member]
Property, plant and equipment at cost:
Property, plant and equipment, at cost	15,057.4	14,743.6
Forestlands and Mineral Rights [Member]
Property, plant and equipment at cost:
Property, plant and equipment, at cost	146.4	144.0
Transportation Equipment [Member]
Property, plant and equipment at cost:
Property, plant and equipment, at cost	30.5	31.2
Leasehold Improvements [Member]
Property, plant and equipment at cost:
Property, plant and equipment, at cost	$ 101.1	$ 100.2