Business Acquisitions - Summary of Unaudited Pro Forma Information (Details) - Columbus Recycling and Encore Recycling - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	May 31, 2022	May 31, 2021	May 31, 2022	May 31, 2021
Business Acquisition [Line Items]
Revenues	$ 1,029,000	$ 887,500	$ 2,671,500	$ 2,073,500
Net income	79,000	68,000	173,000	131,500
Net income attributable to SSI shareholders	$ 78,000	$ 66,500	$ 170,500	$ 127,500