Supplemental Information (Other Noncurrent Assets) (Details) - USD ($) $ in Millions	Sep. 30, 2025	Sep. 30, 2024
Disclosure Text Block Supplement [Abstract]
Pension benefits	$ 210.9	$ 200.0
Derivative instruments	162.8	48.7
Deferred tax assets	127.9	127.8
Prepaid tax	100.4	41.0
Contract assets	82.3	0.0
Contract fulfillment costs	33.8	0.0
Investments other than equity method	17.4	67.1
Deferred financing fees	3.8	4.6
World Energy deferred project costs	0.0	329.4
Other	282.0	352.9
Other noncurrent assets	$ 1,021.3	$ 1,171.5