CONSOLIDATED STATEMENTS OF EARNINGS - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	May. 31, 2015	May. 31, 2014	May. 31, 2015	May. 31, 2014
Income Statement [Abstract]
Net sales	$ 1,506,002	$ 1,738,593	$ 4,577,109	$ 4,953,129
Costs and expenses:
Cost of goods sold	1,270,044	1,560,174	3,933,516	4,455,481
Selling, general and administrative expenses	110,347	121,402	333,332	336,334
Interest expense	20,519	18,849	58,828	57,234
Total costs and expenses	1,400,910	1,700,425	4,325,676	4,849,049
Earnings from continuing operations before income taxes	105,092	38,168	251,433	104,080
Income taxes	37,964	13,700	84,252	32,657
Earnings from continuing operations	67,128	24,468	167,181	71,423
Earnings (loss) from discontinued operations before income taxes (benefit)	(10,871)	(1,042)	(20,241)	17,969
Income taxes (benefit)	(424)	(137)	(445)	8,766
Earnings (loss) from discontinued operations	(10,447)	(905)	(19,796)	9,203
Net earnings	56,681	23,563	147,385	80,626
Less net earnings attributable to noncontrolling interests	0	0	0	1
Net earnings attributable to CMC	$ 56,681	$ 23,563	$ 147,385	$ 80,625
Basic earnings (loss) per share attributable to CMC:
Earnings from continuing operations (in USD per share)	$ 0.58	$ 0.21	$ 1.43	$ 0.61
Earnings (loss) from discontinued operations (in USD per share)	(0.09)	(0.01)	(0.17)	0.08
Net earnings (in USD per share)	0.49	0.20	1.26	0.69
Diluted earnings (loss) per share attributable to CMC:
Earnings from continuing operations (in USD per share)	0.58	0.21	1.42	0.60
Earnings (loss) from discontinued operations (in USD per share)	(0.09)	(0.01)	(0.17)	0.08
Net earnings (in USD per share)	0.49	0.20	1.25	0.68
Cash dividends per share (in USD per share)	$ 0.12	$ 0.12	$ 0.36	$ 0.36
Average basic shares outstanding	115,742,534	117,705,133	116,807,469	117,400,198
Average diluted shares outstanding	116,759,215	118,769,675	117,871,228	118,521,816