Income Taxes - Narrative (Details) - USD ($) $ in Thousands	12 Months Ended
	Aug. 31, 2020	Aug. 31, 2019	Aug. 31, 2018
Operating Loss Carryforwards [Line Items]
Income tax benefit	$ (36,731)	$ (12,456)	$ (104,076)
Deferred Tax Liabilities, Net	139,343	142,900
Income (Loss) from Continuing Operations before Income Taxes, Domestic	324,400	825,700	717,400
Income (Loss) from Continuing Operations before Income Taxes, Foreign	$ 62,500	$ (3,100)	$ (46,200)
Statutory federal income tax rate	21.00%	21.00%	25.70%
Operating Loss Carryforwards	$ 576,600
Deferred Tax Assets, Operating Loss Carryforwards, Subject to Expiration	366,900
Amount of unrecognized tax benefits that would benefit effective tax rate	111,300
Unrecognized Tax Benefits, Interest on Income Taxes Expense	1,000	$ 1,700
Unrecognized Tax Benefits, Interest on Income Taxes Accrued	1,000	2,900
Unrecognized Tax Benefits, Income Tax Penalties and Interest Expense	0
State tax credit
Operating Loss Carryforwards [Line Items]
Tax credit carryforward, amount	125,500
Low sulfer diesel credits
Operating Loss Carryforwards [Line Items]
Tax credit carryforward, amount	59,100
NCRA | State tax credit
Operating Loss Carryforwards [Line Items]
Tax credit carryforward, amount	$ 125,500	$ 123,300