STOCKHOLDERS EQUITY AND EARNINGS PER SHARE (Calculations of the Basic and Diluted Earnings Per Share) (Details) - USD ($) $ / shares in Units, $ in Thousands		3 Months Ended		6 Months Ended
		Feb. 29, 2020	Feb. 28, 2019	Feb. 29, 2020	Feb. 28, 2019
Earnings Per Share [Abstract]
Earnings from continuing operations		$ 63,596	$ 14,928	$ 146,351	$ 34,348
Basic earnings per share:
Shares outstanding for basic earnings per share (shares)		118,919,455	117,854,335	118,644,823	117,677,422
Basic earnings per share attributable to CMC: (in USD per share)	[1]	$ 0.53	$ 0.13	$ 1.23	$ 0.29
Diluted earnings per share:
Shares outstanding for basic earnings per share (shares)		118,919,455	117,854,335	118,644,823	117,677,422
Effect of dilutive securities:
Stock-based incentive/purchase plans (shares)		1,487,801	1,088,423	1,658,436	1,319,005
Shares outstanding for diluted earnings per share (shares)		120,407,256	118,942,758	120,303,259	118,996,427
Diluted earnings per share attributable to CMC: (in USD per share)	[1]	$ 0.53	$ 0.13	$ 1.22	$ 0.29
Antidilutive (shares)				0	0

[1] *Earnings Per Share ("EPS") is calculated independently for each component and may not sum to Net EPS due to rounding