Commitments and Contingencies - Summary of Environmental Reserve Activity (Details) - USD ($) $ in Millions	12 Months Ended
	Nov. 30, 2015	Nov. 30, 2014	Nov. 30, 2013
Accrual for Environmental Loss Contingencies [Roll Forward]
Beginning balance	$ 166.0	$ 171.3	$ 189.5
Additions	176.6	33.7	18.8
Expenditures	(36.5)	(39.0)	(37.0)
Ending balance	306.1	166.0	171.3
Aerojet Rocketdyne- Sacramento [Member]
Accrual for Environmental Loss Contingencies [Roll Forward]
Beginning balance	130.4	128.0	140.5
Additions	44.3	24.0	9.8
Expenditures	(21.7)	(21.6)	(22.3)
Ending balance	153.0	130.4	128.0
Aerojet Rocketdyne- BPOU [Member]
Accrual for Environmental Loss Contingencies [Roll Forward]
Beginning balance	21.7	26.9	31.2
Additions	129.7	4.5	5.1
Expenditures	(11.3)	(9.7)	(9.4)
Ending balance	140.1	21.7	26.9
Other Aerojet Rocketdyne Sites [Member]
Accrual for Environmental Loss Contingencies [Roll Forward]
Beginning balance	8.1	8.2	10.8
Additions	2.0	3.3	0.1
Expenditures	(2.3)	(3.4)	(2.7)
Ending balance	7.8	8.1	8.2
Total Aerojet Rocketdyne [Member]
Accrual for Environmental Loss Contingencies [Roll Forward]
Beginning balance	160.2	163.1	182.5
Additions	176.0	31.8	15.0
Expenditures	(35.3)	(34.7)	(34.4)
Ending balance	300.9	160.2	163.1
Other [Member]
Accrual for Environmental Loss Contingencies [Roll Forward]
Beginning balance	5.8	8.2	7.0
Additions	0.6	1.9	3.8
Expenditures	(1.2)	(4.3)	(2.6)
Ending balance	$ 5.2	$ 5.8	$ 8.2