Commitments and Contingencies - Summary of Environmental Reserve Activity (Details) $ in Millions	6 Months Ended
	May. 31, 2015 USD ($)
Accrual for Environmental Loss Contingencies [Roll Forward]
Beginning balance	$ 166.0
Additions	11.6
Expenditures	(16.1)
Ending balance	161.5
Aerojet Rocketdyne- Sacramento [Member]
Accrual for Environmental Loss Contingencies [Roll Forward]
Beginning balance	130.4
Additions	11.8
Expenditures	(9.0)
Ending balance	133.2
Aerojet Rocketdyne- BPOU [Member]
Accrual for Environmental Loss Contingencies [Roll Forward]
Beginning balance	21.7
Additions	(0.7)
Expenditures	(5.5)
Ending balance	15.5
Other Aerojet Rocketdyne Sites [Member]
Accrual for Environmental Loss Contingencies [Roll Forward]
Beginning balance	8.1
Additions	0.3
Expenditures	(1.1)
Ending balance	7.3
Total Aerojet Rocketdyne [Member]
Accrual for Environmental Loss Contingencies [Roll Forward]
Beginning balance	160.2
Additions	11.4
Expenditures	(15.6)
Ending balance	156.0
Other [Member]
Accrual for Environmental Loss Contingencies [Roll Forward]
Beginning balance	5.8
Additions	0.2
Expenditures	(0.5)
Ending balance	$ 5.5