Note 6 - Investments in Joint Ventures (Details) - Condensed Balance Sheet of EXCOR and NTI ASEAN, and All Other Joint Ventures (USD $)	Nov. 30, 2014	Aug. 31, 2014
Condensed Balance Sheet Statements, Captions [Line Items]
Current assets	$ 63,676,926	$ 61,491,957
Total assets	67,341,357	65,466,964
Current liabilities	18,187,978	17,542,634
Noncurrent liabilities	2,497,563	1,929,488
Joint ventures’ equity	46,655,816	45,994,842
Northern Technologies International Corporation’s share of joint ventures’ equity	23,302,301	22,961,989
Northern Technologies International Corporation’s share of joint ventures’ undistributed earnings	21,178,153	20,540,523
EXCOR [Member]
Condensed Balance Sheet Statements, Captions [Line Items]
Current assets	25,235,772	24,361,157
Total assets	27,164,361	26,652,165
Current liabilities	3,334,169	3,512,143
Joint ventures’ equity	23,830,192	23,140,022
Northern Technologies International Corporation’s share of joint ventures’ equity	11,915,098	11,570,013
Northern Technologies International Corporation’s share of joint ventures’ undistributed earnings	11,884,193	11,539,108
China [Member]
Condensed Balance Sheet Statements, Captions [Line Items]
Current assets	10,271,450	9,774,680
Total assets	10,289,207	9,793,803
Current liabilities	4,665,093	4,438,380
Noncurrent liabilities	868,779	868,377
Joint ventures’ equity	4,755,335	4,487,046
Northern Technologies International Corporation’s share of joint ventures’ equity	2,377,668	2,243,524
Northern Technologies International Corporation’s share of joint ventures’ undistributed earnings	2,327,668	2,193,524
All Other [Member]
Condensed Balance Sheet Statements, Captions [Line Items]
Current assets	28,169,704	27,356,120
Total assets	29,887,789	29,020,996
Current liabilities	10,188,716	9,592,111
Noncurrent liabilities	1,628,784	1,061,111
Joint ventures’ equity	18,070,289	18,367,775
Northern Technologies International Corporation’s share of joint ventures’ equity	9,009,535	9,148,452
Northern Technologies International Corporation’s share of joint ventures’ undistributed earnings	$ 6,966,292	$ 6,807,891

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