Commitments and Contingencies - Summary of Environmental Reserve Activity (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Feb. 28, 2014
Commitment And Contingencies [Line Items]
Environmental reserve, Beginning Balance	$ 171.3
Additions	7.2
Expenditures	(8.1)
Environmental reserve, Ending Balance	170.4
Aerojet Rocketdyne- Sacramento [Member]
Commitment And Contingencies [Line Items]
Environmental reserve, Beginning Balance	128.0
Additions	4.1
Expenditures	(3.5)
Environmental reserve, Ending Balance	128.6
Aerojet Rocketdyne- BPOU [Member]
Commitment And Contingencies [Line Items]
Environmental reserve, Beginning Balance	26.9
Additions	0.9
Expenditures	(1.4)
Environmental reserve, Ending Balance	26.4
Other Aerojet Rocketdyne Sites [Member]
Commitment And Contingencies [Line Items]
Environmental reserve, Beginning Balance	8.2
Additions	1.5
Expenditures	(0.9)
Environmental reserve, Ending Balance	8.8
Total Aerojet Rocketdyne [Member]
Commitment And Contingencies [Line Items]
Environmental reserve, Beginning Balance	163.1
Additions	6.5
Expenditures	(5.8)
Environmental reserve, Ending Balance	163.8
Other [Member]
Commitment And Contingencies [Line Items]
Environmental reserve, Beginning Balance	8.2
Additions	0.7
Expenditures	(2.3)
Environmental reserve, Ending Balance	$ 6.6