CONDENSED CONSOLIDATED STATEMENTS OF EARNINGS (UNAUDITED) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Feb. 28, 2018	Feb. 28, 2017	Feb. 28, 2018	Feb. 28, 2017
Income Statement [Abstract]
Net sales	$ 1,054,268	$ 862,298	$ 2,130,801	$ 1,715,226
Costs and expenses:
Cost of goods sold	927,101	725,051	1,860,617	1,461,590
Selling, general and administrative expenses	108,477	94,044	204,587	188,969
Interest expense	7,181	12,439	13,792	25,764
Total costs and expenses	1,042,759	831,534	2,078,996	1,676,323
Earnings from continuing operations before income taxes	11,509	30,764	51,805	38,903
Income taxes	1,728	7,772	10,153	10,225
Earnings from continuing operations	9,781	22,992	41,652	28,678
Earnings from discontinued operations before income taxes (benefit)	290	9,591	8,410	10,362
Income taxes (benefit)	(98)	2,251	3,082	2,433
Earnings from discontinued operations	388	7,340	5,328	7,929
Net earnings	$ 10,169	$ 30,332	$ 46,980	$ 36,607
Basic earnings per share attributable to CMC
Earnings from continuing operations (in USD per share)	$ 0.08	$ 0.20	$ 0.36	$ 0.25
Earnings (loss) from discontinued operations (in USD per share)	0.00	0.06	0.05	0.07
Net earnings (in USD per share)	0.09	0.26	0.40	0.32
Diluted earnings per share attributable to CMC
Earnings from continuing operations (in USD per share)	0.08	0.20	0.35	0.25
Earnings (loss) from discontinued operations (in USD per share)	0.00	0.06	0.05	0.07
Net earnings (in USD per share)	0.09	0.26	0.40	0.31
Cash dividends per share (in USD per share)	$ 0.12	$ 0.12	$ 0.24	$ 0.24
Average basic shares outstanding	116,808,838	115,736,369	116,524,630	115,415,662
Average diluted shares outstanding	118,269,721	117,120,208	118,149,815	117,007,958