Revisions - Summary of Impact of Errors to Unaudited Condensed Consolidated Statement of Operation (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended				6 Months Ended		9 Months Ended
	May. 31, 2015	Aug. 31, 2014	May. 31, 2014	Feb. 28, 2014	May. 31, 2015	May. 31, 2014	Aug. 31, 2014
Statement of Operations:
Net sales	$ 456.9	$ 421.2	$ 404.5	$ 332.1	$ 775.5	$ 736.6
Cost of sales (exclusive of items shown separately on Statement of Operations)	372.5	376.5	369.4	288.5	655.3	657.9
Selling, general and administrative	12.6	9.7	9.2	9.2	28.1	18.4
Depreciation and amortization	16.1	15.8	15.7	14.9	32.1	30.6	$ 46.4
Other expense, net		16.3	48.3	7.6
Operating income (loss)	52.9	2.9	(38.1)	11.9	55.5	(26.2)
Total non-operating expenses, net	13.2	14.0	12.6	12.4	26.5	25.0
Loss from continuing operations before income taxes	39.7	(11.1)	(50.7)	(0.5)	29.0	(51.2)
Loss from continuing operations	18.4	(10.1)	(50.1)	(2.3)	14.3	(52.4)
(Loss) income from discontinued operations, net of income taxes	0.0	0.2	(0.8)	0.0	0.2	(0.8)	(0.6)
Net income (loss)	$ 18.4	$ (9.9)	$ (50.9)	$ (2.3)	$ 14.5	$ (53.2)	(63.1)
Basic and diluted loss per share:
Loss per share from continuing operations (in USD per share)	$ 0.29	$ (0.18)	$ (0.87)	$ (0.04)	$ 0.23	$ (0.90)
Loss per share from discontinued operations, net of income taxes (in USD per share)	0.00	0.00	(0.01)	0.00	0.00	(0.01)
Net loss per share (in USD per share)	$ 0.29	$ (0.18)	$ (0.88)	$ (0.04)	$ 0.23	$ (0.91)
Previously Reported [Member]
Statement of Operations:
Net sales		$ 419.5	$ 403.1	$ 329.7
Cost of sales (exclusive of items shown separately on Statement of Operations)		374.2	367.0	286.0
Selling, general and administrative		9.7	9.2	9.2
Depreciation and amortization		15.7	15.4	14.8		$ 30.2	45.9
Other expense, net		16.3	48.5	7.4
Operating income (loss)		3.6	(37.0)	12.3
Total non-operating expenses, net		14.0	12.6	12.4
Loss from continuing operations before income taxes		(10.4)	(49.6)	(0.1)
Loss from continuing operations		(9.7)	(49.4)	(2.1)
(Loss) income from discontinued operations, net of income taxes		0.2	(0.8)	0.0		(0.8)	(0.6)
Net income (loss)		$ (9.5)	$ (50.2)	$ (2.1)		$ (52.3)	$ (61.8)
Basic and diluted loss per share:
Loss per share from continuing operations (in USD per share)		$ (0.17)	$ (0.86)	$ (0.03)
Loss per share from discontinued operations, net of income taxes (in USD per share)		0.00	(0.01)	0.00
Net loss per share (in USD per share)		$ (0.17)	$ (0.87)	$ (0.03)