Income Taxes - Narrative (Details) - USD ($) $ in Millions	12 Months Ended
	Aug. 31, 2017	Aug. 31, 2016	Aug. 31, 2015
Operating Loss Carryforwards [Line Items]
Income (Loss) from Continuing Operations before Income Taxes, Domestic	$ 213.8	$ 490.8	$ 824.9
Income (Loss) from Continuing Operations before Income Taxes, Foreign	(268.7)	(70.9)	(56.7)
Unrecognized Tax Benefits, Income Tax Penalties and Interest Expense	0.0	0.0	$ 0.0
Operating Loss Carryforwards	689.2
Deferred Tax Assets, Operating Loss Carryforwards, Subject to Expiration	458.1
Change in valuation allowance for deferred tax asset	61.9
Unrecognized Tax Benefits, Income Tax Penalties and Interest Accrued	0.0	0.0
Other Assets [Member]
Operating Loss Carryforwards [Line Items]
Deferred Tax Assets, Net of Valuation Allowance, Noncurrent	0.7	2.5
Alternative Minimum Tax Credit [Member]
Operating Loss Carryforwards [Line Items]
Tax credit carryforward, amount	8.1
General Business Tax Credit Carryforward [Member]
Operating Loss Carryforwards [Line Items]
Tax credit carryforward, amount	60.0
State tax credits [Member]
Operating Loss Carryforwards [Line Items]
Tax credit carryforward, amount	172.9
NCRA [Member]
Operating Loss Carryforwards [Line Items]
Change in valuation allowance for deferred tax asset	26.6
NCRA [Member] | State tax credits [Member]
Operating Loss Carryforwards [Line Items]
Tax credit carryforward, amount	$ 172.9	$ 133.5