Commitments and Contingencies - Summary of Environmental Reserve Activity (Detail) (USD $) In Millions, unless otherwise specified	6 Months Ended
	May 31, 2014
Site Contingency [Line Items]
Environmental reserve, Beginning Balance	$ 171.3
Additions	10.3
Expenditures	(17.9)
Environmental reserve, Ending Balance	163.7
Aerojet Rocketdyne- Sacramento [Member]
Site Contingency [Line Items]
Environmental reserve, Beginning Balance	128.0
Additions	6.7
Expenditures	(10.1)
Environmental reserve, Ending Balance	124.6
Aerojet Rocketdyne- BPOU [Member]
Site Contingency [Line Items]
Environmental reserve, Beginning Balance	26.9
Additions	0.6
Expenditures	(3.8)
Environmental reserve, Ending Balance	23.7
Other Aerojet Rocketdyne Sites [Member]
Site Contingency [Line Items]
Environmental reserve, Beginning Balance	8.2
Additions	2.3
Expenditures	(1.8)
Environmental reserve, Ending Balance	8.7
Total Aerojet Rocketdyne [Member]
Site Contingency [Line Items]
Environmental reserve, Beginning Balance	163.1
Additions	9.6
Expenditures	(15.7)
Environmental reserve, Ending Balance	157.0
Other [Member]
Site Contingency [Line Items]
Environmental reserve, Beginning Balance	8.2
Additions	0.7
Expenditures	(2.2)
Environmental reserve, Ending Balance	$ 6.7