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, 2019	May 31, 2018	May 31, 2019	May 31, 2018
Earnings Per Share [Abstract]
Earnings from continuing operations		$ 78,551	$ 42,325	$ 112,899	$ 83,977
Basic earnings per share:
Shares outstanding for basic earnings per share (shares)		118,045,362	117,111,799	117,762,945	116,722,504
Basic earnings per share attributable to CMC: (in USD per share)	[1]	$ 0.67	$ 0.36	$ 0.96	$ 0.72
Diluted earnings per share:
Shares outstanding for basic earnings per share (shares)		118,045,362	117,111,799	117,762,945	116,722,504
Effect of dilutive securities:
Stock-based incentive/purchase plans (shares)		1,100,204	1,142,992	1,250,069	1,328,360
Shares outstanding for diluted earnings per share (shares)		119,145,566	118,254,791	119,013,014	118,050,864
Diluted earnings per share attributable to CMC: (in USD per share)	[1]	$ 0.66	$ 0.36	$ 0.95	$ 0.71
Antidilutive (shares)		32,623	26,886

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