Consolidated Statements of Income - USD ($) shares in Thousands, $ in Thousands		12 Months Ended
		Aug. 31, 2019	Aug. 31, 2018	Aug. 31, 2017
Income Statement [Abstract]
Revenues		$ 2,132,781	$ 2,364,715	$ 1,687,591
Operating expense:
Cost of goods sold		1,858,535	2,010,485	1,464,508
Selling, general and administrative		191,405	208,877	171,570
(Income) from joint ventures		(1,452)	(1,953)	(3,674)
Asset impairment charges (recoveries), net		63	(1,021)	(717)
Restructuring charges and other exit-related activities		365	(661)	(109)
Operating income		83,865	148,988	56,013
Interest expense		(8,266)	(8,983)	(8,081)
Other income, net		641	1,848	758
Income from continuing operations before income taxes		76,240	141,853	48,690
Income tax (expense) benefit		(17,670)	17,590	(1,322)
Income from continuing operations		58,570	159,443	47,368
(Loss) income from discontinued operations, net of tax		(248)	346	(390)
Net income		58,322	159,789	46,978
Net income attributable to noncontrolling interests		(1,977)	(3,338)	(2,467)
Net income attributable to SSI shareholders		$ 56,345	$ 156,451	$ 44,511
Net income per share attributable to SSI shareholders Basic:
Income per share from continuing operations		$ 2.06	$ 5.65	$ 1.63
(Loss) income per share from discontinued operations		(0.01)	0.01	(0.01)
Net income per share		2.05	5.66	1.62
Net income per share attributable to SSI shareholders Diluted:
Income per share from continuing operations		2.01	5.46	1.60
(Loss) income per share from discontinued operations		(0.01)	0.01	(0.01)
Net income per share	[1]	$ 2.00	$ 5.47	$ 1.58
Weighted average number of common shares:
Basic		27,527	27,645	27,537
Diluted		28,222	28,589	28,141

[1] May not foot due to rounding.