Revenue Recognition (Contract Assets and Liabilities) (Details) - USD ($) $ in Millions	6 Months Ended
	Mar. 31, 2026	Sep. 30, 2025
Contract Assets and Liabilities
Contract assets – current	$ 97.8	$ 152.6
Contract fulfillment costs – current	85.2	85.4
Contract assets – noncurrent	106.8	82.3
Contract fulfillment costs – noncurrent	35.1	33.8
Contract liabilities – current	247.8	253.4
Contract liabilities – noncurrent	283.7	$ 283.6
Revenue recognized that was previously included in current contract liabilities	$ 120.0