Restatement - Schedule of Effects of Prior Period Errors on the Consolidated Financial Statements - Consolidated Statements of Comprehensive (Loss) Income (Details) - USD ($) $ 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
Error Corrections and Prior Period Adjustments Restatement [Line Items]
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
Other comprehensive (loss) income:
Amortization of net actuarial losses, net of income taxes		11.8	12.3	12.1	7.4	7.7	7.8	7.7	24.4	15.5	36.2	23.2	49.4	31.1	91.3
Actuarial losses and prior service costs arising during the period, net of income taxes				0.0	(136.0)								(56.6)	(136.0)	167.6
Amortization of prior service credits, net of income taxes													(0.8)	(0.5)	(0.9)
Comprehensive (loss) income		(26.1)	29.6	8.8	(116.7)	(2.8)	(41.4)	5.5	38.4	(35.9)	12.3	(38.7)	$ (24.2)	(155.4)	420.9
As Reported [Member]
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Net (loss) income		(38.1)	18.4	(3.9)	10.1	(9.9)	(50.9)	(2.3)	14.5	(53.2)	(23.6)	(63.1)		(53.0)	167.9
Other comprehensive (loss) income:
Amortization of net actuarial losses, net of income taxes		11.6	12.2	12.2	7.5	7.5	7.7	7.5	24.4	15.2	36.0	22.7		30.7	91.3
Actuarial losses and prior service costs arising during the period, net of income taxes				0.0	(142.0)									(142.0)	173.5
Amortization of prior service credits, net of income taxes														(0.5)	(0.9)
Comprehensive (loss) income		(26.5)	30.6	8.3	(124.4)	(2.4)	(43.2)	5.2	38.9	(38.0)	12.4	(40.4)		(164.8)	431.8
Adjustments [Member]
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Net (loss) income		0.2	(1.1)	0.6	1.8	(0.6)	1.7	0.1	(0.5)	1.8	(0.3)	1.2		3.0	(5.0)
Other comprehensive (loss) income:
Amortization of net actuarial losses, net of income taxes		0.2	0.1	(0.1)	(0.1)	0.2	0.1	0.2	0.0	0.3	0.2	0.5		0.4	0.0
Actuarial losses and prior service costs arising during the period, net of income taxes				0.0	6.0									6.0	(5.9)
Amortization of prior service credits, net of income taxes														0.0	0.0
Comprehensive (loss) income		$ 0.4	$ (1.0)	$ 0.5	$ 7.7	$ (0.4)	$ 1.8	$ 0.3	$ (0.5)	$ 2.1	$ (0.1)	$ 1.7		$ 9.4	$ (10.9)