Commitments and Contingencies - Summary of Environmental Reserve Activity (Details) $ in Millions	9 Months Ended
	Aug. 31, 2015 USD ($)
Accrual for Environmental Loss Contingencies [Roll Forward]
Beginning balance	$ 166.0
Additions	93.3
Expenditures	(23.2)
Ending balance	236.1
Aerojet Rocketdyne- Sacramento [Member]
Accrual for Environmental Loss Contingencies [Roll Forward]
Beginning balance	130.4
Additions	27.0
Expenditures	(13.7)
Ending balance	143.7
Aerojet Rocketdyne- BPOU [Member]
Accrual for Environmental Loss Contingencies [Roll Forward]
Beginning balance	21.7
Additions	64.0
Expenditures	(7.2)
Ending balance	78.5
Other Aerojet Rocketdyne Sites [Member]
Accrual for Environmental Loss Contingencies [Roll Forward]
Beginning balance	8.1
Additions	1.9
Expenditures	(1.6)
Ending balance	8.4
Total Aerojet Rocketdyne [Member]
Accrual for Environmental Loss Contingencies [Roll Forward]
Beginning balance	160.2
Additions	92.9
Expenditures	(22.5)
Ending balance	230.6
Other [Member]
Accrual for Environmental Loss Contingencies [Roll Forward]
Beginning balance	5.8
Additions	0.4
Expenditures	(0.7)
Ending balance	$ 5.5