Income Taxes - Rollforward of Unrecognized Tax Benefits (Details) - USD ($) $ in Thousands	12 Months Ended
	Aug. 31, 2018	Aug. 31, 2017	Aug. 31, 2016
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Balance at beginning of period	$ 37,830	$ 37,105	$ 72,181
Additions attributable to current year tax positions	3,640	725	1,387
Additions attributable to prior year tax positions	49,665	0	0
Reductions attributable to prior year tax positions	0	0	(36,463)
Balance at end of period	$ 91,135	$ 37,830	$ 37,105