Note 6 - Condensed Balance Sheet of EXCOR and All Other Joint Ventures (Details) - USD ($)	Nov. 30, 2015	Aug. 31, 2015
EXCOR [Member]
Current assets	$ 25,060,815	$ 22,620,323
Total assets	26,925,906	24,606,880
Current liabilities	$ 3,612,595	$ 3,360,142
Noncurrent liabilities
Joint ventures’ equity	$ 23,313,311	$ 21,246,738
Northern Technologies International Corporation’s share of joint ventures’ equity	11,656,658	11,571,361
Northern Technologies International Corporation’s share of joint ventures’ undistributed earnings	11,625,753	11,540,456
All Other [Member]
Current assets	25,310,781	26,674,793
Total assets	26,957,272	28,247,058
Current liabilities	9,335,724	8,928,241
Noncurrent liabilities	89,930	1,215,139
Joint ventures’ equity	17,531,619	18,103,679
Northern Technologies International Corporation’s share of joint ventures’ equity	8,712,344	8,972,877
Northern Technologies International Corporation’s share of joint ventures’ undistributed earnings	6,682,388	6,942,921
Current assets	50,371,596	49,295,116
Total assets	53,883,178	52,853,938
Current liabilities	12,948,319	12,288,383
Noncurrent liabilities	89,930	1,215,139
Joint ventures’ equity	40,844,930	39,350,417
Northern Technologies International Corporation’s share of joint ventures’ equity	20,369,002	20,544,238
Northern Technologies International Corporation’s share of joint ventures’ undistributed earnings	$ 18,308,141	$ 18,483,377