Unusual Items - Summary of Loss Incurred on Repurchase of Debt Instruments (Details) - USD ($) $ in Millions	3 Months Ended							6 Months Ended		9 Months Ended		12 Months Ended
	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
Unusual or Infrequent Item [Line Items]
Loss on 4 1/16% Debentures repurchased	$ (1.1)	$ (0.5)	$ (0.2)	$ 0.0	$ (9.8)	$ (45.9)	$ (4.9)	$ (0.7)	$ (50.8)	$ (1.8)	$ (60.6)	$ (1.9)	$ (60.6)	$ (5.0)
4.0625% Convertible Subordinated Debentures [Member]
Unusual or Infrequent Item [Line Items]
Principal amount repurchased													59.6	5.2
Cash repurchase price													(119.9)	(10.1)
Write-off of deferred financing costs													(0.3)	(0.1)
Loss on 4 1/16% Debentures repurchased													$ (60.6)	$ (5.0)