Commitments and Contingencies and Derivative Financial Instruments (Details) $ in Millions, $ in Millions				6 Months Ended	12 Months Ended
	Feb. 13, 2023 USD ($)	Apr. 12, 2022 USD ($)	Apr. 12, 2022 AUD ($)	Mar. 29, 2024 USD ($)	Sep. 29, 2023 USD ($)	Sep. 30, 2022 USD ($) derivative_agreement	Oct. 02, 2020 USD ($)	Sep. 28, 2012 MW	Dec. 22, 2008 case
Loss Contingencies [Line Items]
Recorded third-party environmental recoveries receivable						$ 27.0
JKC Australia LNG Pty Limited
Loss Contingencies [Line Items]
Settlement payment		$ 475.0
General Electric and GE Electrical International Inc
Loss Contingencies [Line Items]
Plant capacity (in MW's) | MW								360
Settlement payment			$ 640
Litigation expenses included in segment profit						$ 91.3
Kingston Power Plant of the TVA, Secondary Case No. 3:13CV-505-TAV-HBG
Loss Contingencies [Line Items]
Number of pending claims | case									10
UGL Infrastructure Pty Limited | Consortium Agreement
Loss Contingencies [Line Items]
Percentage of ownership interest in joint venture								50.00%
Surety Bond
Loss Contingencies [Line Items]
Aggregate principal balance of short-term debt				$ 2,200.0	$ 2,000.0
LOCs
Loss Contingencies [Line Items]
Aggregate principal balance of short-term debt				289.7	322.0
Treasury Lock
Loss Contingencies [Line Items]
Number of instruments held | derivative_agreement						2
Derivative notional amount						$ 500.0
Gain on derivatives, before taxes	$ 37.4
Unrealized gain (loss) on derivatives				25.1	26.5
Treasury Lock | Fixed Rate Date
Loss Contingencies [Line Items]
Derivative fixed interest rate	5.90%
Aggregate principal amount	$ 500.0				500.0
Interest Rate Swap
Loss Contingencies [Line Items]
Derivative notional amount				745.9
Unrealized gain (loss) on derivatives				59.6	77.2
Derivative assets (liabilities), at fair value				79.1	102.6
Interest Rate Swap | Other Current Assets
Loss Contingencies [Line Items]
Derivative assets (liabilities), at fair value				12.9
Interest Rate Swap | Total Other Non-current Assets
Loss Contingencies [Line Items]
Derivative assets (liabilities), at fair value				$ 66.2
Interest Rate Swap | Minimum
Loss Contingencies [Line Items]
Term of derivative contract				5 years
Interest Rate Swap | Maximum
Loss Contingencies [Line Items]
Term of derivative contract				10 years
Cross Currency Interest Rate Contract
Loss Contingencies [Line Items]
Derivative notional amount							$ 127.8
Cross Currency Interest Rate Contract | Minimum
Loss Contingencies [Line Items]
Term of derivative contract				3 years 6 months
Foreign Exchange Forward
Loss Contingencies [Line Items]
Derivative notional amount				$ 946.1	857.7
Derivative assets (liabilities), at fair value				(4.3)	9.5
Foreign Exchange Forward | Current Liabilities
Loss Contingencies [Line Items]
Derivative assets (liabilities), at fair value				(4.9)	(6.6)
Foreign Exchange Forward | Current Assets
Loss Contingencies [Line Items]
Derivative assets (liabilities), at fair value				$ 0.6	$ 16.1
Foreign Exchange Forward | Minimum
Loss Contingencies [Line Items]
Term of derivative contract				7 days
Foreign Exchange Forward | Maximum
Loss Contingencies [Line Items]
Term of derivative contract				10 months