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		9 Months Ended
		May 31, 2020	May 31, 2019	May 31, 2020	May 31, 2019
Earnings Per Share [Abstract]
Earnings from continuing operations		$ 64,169	$ 78,551	$ 210,520	$ 112,899
Basic earnings per share:
Shares outstanding for basic earnings per share (shares)		119,192,962	118,045,362	118,828,870	117,762,945
Basic earnings per share attributable to CMC: (in USD per share)	[1]	$ 0.54	$ 0.67	$ 1.77	$ 0.96
Diluted earnings per share:
Shares outstanding for basic earnings per share (shares)		119,192,962	118,045,362	118,828,870	117,762,945
Effect of dilutive securities:
Stock-based incentive/purchase plans (shares)		1,085,779	1,100,204	1,448,867	1,250,069
Shares outstanding for diluted earnings per share (shares)		120,278,741	119,145,566	120,277,737	119,013,014
Diluted earnings per share attributable to CMC: (in USD per share)	[1]	$ 0.53	$ 0.66	$ 1.75	$ 0.95

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