Commitments and Contingencies - Summary of Environmental Reserve Activity (Detail) (USD $) In Millions, unless otherwise specified	9 Months Ended
	Aug. 31, 2014
Accrual for Environmental Loss Contingencies [Roll Forward]
Beginning balance	$ 171.3
Additions	25.5
Expenditures	(28.2)
Ending balance	168.6
Aerojet Rocketdyne- Sacramento [Member]
Accrual for Environmental Loss Contingencies [Roll Forward]
Beginning balance	128.0
Additions	17.6
Expenditures	(15.4)
Ending balance	130.2
Aerojet Rocketdyne- BPOU [Member]
Accrual for Environmental Loss Contingencies [Roll Forward]
Beginning balance	26.9
Additions	3.7
Expenditures	(6.8)
Ending balance	23.8
Other Aerojet Rocketdyne Sites [Member]
Accrual for Environmental Loss Contingencies [Roll Forward]
Beginning balance	8.2
Additions	2.6
Expenditures	(2.8)
Ending balance	8.0
Total Aerojet Rocketdyne [Member]
Accrual for Environmental Loss Contingencies [Roll Forward]
Beginning balance	163.1
Additions	23.9
Expenditures	(25.0)
Ending balance	162.0
Other [Member]
Accrual for Environmental Loss Contingencies [Roll Forward]
Beginning balance	8.2
Additions	1.6
Expenditures	(3.2)
Ending balance	$ 6.6