Income Taxes - Narrative (Details) - USD ($) $ in Thousands	3 Months Ended								6 Months Ended		9 Months Ended		12 Months Ended
	Aug. 31, 2018	May 31, 2018	Feb. 28, 2018	Nov. 30, 2017	Aug. 31, 2017	May 31, 2017	Feb. 28, 2017	Nov. 30, 2016	Feb. 28, 2018	Feb. 28, 2017	May 31, 2018	May 31, 2017	Aug. 31, 2018	Aug. 31, 2017	Aug. 31, 2016
Operating Loss Carryforwards [Line Items]
Income tax expense (benefit)	$ 7,787	$ 55,219	$ (187,688)	$ 20,606	$ (34,761)	$ (166,124)	$ 3,685	$ 16,076	$ (167,082)	$ 19,761	$ (111,863)	$ (146,363)	$ (104,076)	$ (181,124)	$ 19,099
Deferred Tax Liabilities, Net	182,361				328,803								182,361	328,803
Income (Loss) from Continuing Operations before Income Taxes, Domestic													717,400	158,500	473,000
Income (Loss) from Continuing Operations before Income Taxes, Foreign													$ (46,200)	$ (268,700)	$ (70,900)
Statutory federal income tax rate													25.70%	35.00%	35.00%
Tax Act, provisionally recorded net benefit, revaluation of U.S. net deferred tax liability													$ 155,200
Operating Loss Carryforwards	531,100												531,100
Deferred Tax Assets, Operating Loss Carryforwards, Subject to Expiration	342,800												342,800
Change in valuation allowance for deferred tax asset													33,800
Amount of unrecognized tax benefits that would benefit effective tax rate	83,300												83,300
Unrecognized Tax Benefits, Interest on Income Taxes Expense													1,200
Unrecognized Tax Benefits, Interest on Income Taxes Accrued	1,200												1,200
Unrecognized Tax Benefits, Income Tax Penalties and Interest Expense													0	$ 0
Unrecognized Tax Benefits, Income Tax Penalties and Interest Accrued	0												0
Other assets
Operating Loss Carryforwards [Line Items]
Deferred Tax Assets, Net of Valuation Allowance, Noncurrent	400				1,200								400	1,200
State tax credit
Operating Loss Carryforwards [Line Items]
Tax credit carryforward, amount	121,600												121,600
Alternative minimum tax credit
Operating Loss Carryforwards [Line Items]
Tax credit carryforward, amount	6,100												6,100
Low sulfer diesel credits
Operating Loss Carryforwards [Line Items]
Tax credit carryforward, amount	61,200												61,200
NCRA
Operating Loss Carryforwards [Line Items]
Change in valuation allowance for deferred tax asset													17,000
NCRA | State tax credit
Operating Loss Carryforwards [Line Items]
Tax credit carryforward, amount	121,600				172,900								121,600	172,900
Foreign tax authority | Fiscal year 2018
Operating Loss Carryforwards [Line Items]
Tax credit carryforward, amount	$ 11,200												$ 11,200
Restatement Adjustments
Operating Loss Carryforwards [Line Items]
Income tax expense (benefit)		(5,119)	(6,512)	670	9,532	(3,106)	(4,939)	(536)	(5,842)	(5,475)	(10,962)	(8,582)		951	$ 23,190
As Previously Reported
Operating Loss Carryforwards [Line Items]
Income tax expense (benefit)		$ 60,338	$ (181,176)	$ 19,936	(44,293)	$ (163,018)	$ 8,624	$ 16,612	$ (161,240)	$ 25,236	$ (100,901)	$ (137,781)		(182,075)	$ (4,091)
Deferred Tax Liabilities, Net					$ 3,700									$ 3,700