Note 6 - Condensed Balance Sheet of EXCOR and All Other Joint Ventures (Details) - USD ($)	Feb. 29, 2016	Aug. 31, 2015
EXCOR [Member]
Current assets	$ 20,543,914	$ 22,620,323
Total assets	22,412,469	24,606,880
Current liabilities	$ 3,517,274	$ 3,360,142
Noncurrent liabilities
Joint ventures’ equity	$ 18,895,195	$ 21,246,738
Northern Technologies International Corporation’s share of joint ventures’ equity	9,447,599	11,571,361
Northern Technologies International Corporation’s share of joint ventures’ undistributed earnings	9,416,694	11,540,456
All Other [Member]
Current assets	24,371,968	26,674,793
Total assets	26,044,087	28,247,058
Current liabilities	8,828,974	8,928,241
Noncurrent liabilities	89,039	1,215,139
Joint ventures’ equity	17,126,074	18,103,679
Northern Technologies International Corporation’s share of joint ventures’ equity	8,505,397	8,972,877
Northern Technologies International Corporation’s share of joint ventures’ undistributed earnings	6,475,441	6,942,921
Current assets	44,915,882	49,295,116
Total assets	48,456,556	52,853,938
Current liabilities	12,346,248	12,288,383
Noncurrent liabilities	89,039	1,215,139
Joint ventures’ equity	36,021,269	39,350,417
Northern Technologies International Corporation’s share of joint ventures’ equity	17,952,996	20,544,238
Northern Technologies International Corporation’s share of joint ventures’ undistributed earnings	$ 15,892,135	$ 18,483,377