Acquisition, (As Restated for fiscal 2013) - Summary of Pro Forma Information Related to Results of Operations (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended								6 Months Ended		9 Months Ended		12 Months Ended
	Nov. 30, 2015	Aug. 31, 2015	May. 31, 2015	Feb. 28, 2015	Nov. 30, 2014	Aug. 31, 2014	May. 31, 2014	Feb. 28, 2014	May. 31, 2015	May. 31, 2014	Aug. 31, 2015	Aug. 31, 2014	Nov. 30, 2015	Nov. 30, 2014	Nov. 30, 2013
Net sales:
Net sales	$ 486.5	$ 441.0	$ 457.8	$ 323.0	$ 443.6	$ 420.4	$ 406.6	$ 331.6	$ 780.8	$ 738.2	$ 1,221.8	$ 1,158.6	$ 1,708.3	$ 1,602.2	$ 1,378.1
Net income:
Net (loss) income	$ 7.7	$ (37.9)	$ 17.3	$ (3.3)	$ 11.9	$ (10.5)	$ (49.2)	$ (2.2)	$ 14.0	$ (51.4)	$ (23.9)	$ (61.9)	$ (16.2)	$ (50.0)	$ 162.9
Basic income per share
Basic net (loss) income per share (in USD per share)	$ 0.12	$ (0.61)	$ 0.28	$ (0.06)	$ 0.20	$ (0.19)	$ (0.85)	$ (0.04)	$ 0.23				$ (0.27)	$ (0.86)	$ 2.68
Diluted income per share
Diluted net (loss) income per share (in USD per share)	$ 0.12	$ (0.61)	$ 0.25	$ (0.06)	$ 0.18	$ (0.19)	$ (0.85)	$ (0.04)	$ 0.22				$ (0.27)	$ (0.86)	$ 2.05
Rocketdyne Business [Member]
Net sales:
Pro forma															$ 1,757.7
Net income:
Pro forma															$ 25.7
Basic income per share
Pro forma (in USD per share)															$ 0.42
Diluted income per share
Pro forma (in USD per share)															$ 0.41