Revenue Recognition - Narrative (Details) - USD ($) $ in Millions	3 Months Ended
	Dec. 31, 2024	Dec. 31, 2023	Sep. 30, 2024
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Passed through costs included in revenue and cost of sales	$ 2,200.0	$ 2,200.0
Transaction price, allocated	19,100.0
Contract liabilities, revenue recognized	623.5	$ 527.0
Significant claims recorded in contract assets and other non-current assets	170.0		$ 180.0
Trade receivables sold with no financial and legal obligations	$ 353.0		$ 319.5
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2025-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, remaining performance obligation (as percent)	57.00%
Revenue, performance obligation expected timing of satisfaction period	12 months
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2026-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, performance obligation expected timing of satisfaction period	2 years