Commitments and Contingencies - Summary of Environmental Reserve Activity (Details) $ in Millions	3 Months Ended
	Mar. 31, 2023 USD ($)
Accrual for Environmental Loss Contingencies [Roll Forward]
Beginning balance	$ 290.5
Additions/Adjustments	3.1
Expenditures	(8.3)
Ending balance	285.3
Aerojet Rocketdyne- Sacramento
Accrual for Environmental Loss Contingencies [Roll Forward]
Beginning balance	223.6
Additions/Adjustments	4.5
Expenditures	(4.0)
Ending balance	224.1
Aerojet Rocketdyne- BPOU
Accrual for Environmental Loss Contingencies [Roll Forward]
Beginning balance	50.8
Additions/Adjustments	(1.7)
Expenditures	(3.9)
Ending balance	45.2
Other Aerojet Rocketdyne Sites
Accrual for Environmental Loss Contingencies [Roll Forward]
Beginning balance	10.8
Additions/Adjustments	0.2
Expenditures	(0.3)
Ending balance	10.7
Total Aerojet Rocketdyne
Accrual for Environmental Loss Contingencies [Roll Forward]
Beginning balance	285.2
Additions/Adjustments	3.0
Expenditures	(8.2)
Ending balance	280.0
Other
Accrual for Environmental Loss Contingencies [Roll Forward]
Beginning balance	5.3
Additions/Adjustments	0.1
Expenditures	(0.1)
Ending balance	$ 5.3