Note 6 - Condensed Income Statement of EXCOR, Tianjin Zerust, and All Other Joint Ventures (Details) - USD ($)	6 Months Ended
	Feb. 29, 2016	Feb. 28, 2015
EXCOR [Member]
Net sales	$ 15,618,735	$ 18,383,653
Gross profit	8,059,186	9,766,973
Net income	2,960,951	3,924,547
Northern Technologies International Corporation’s share of equity in income of joint ventures	1,480,975	1,962,047
All Other [Member]
Net sales	26,381,689	30,059,128
Gross profit	10,463,916	13,989,900
Net income	911,777	1,961,987
Northern Technologies International Corporation’s share of equity in income of joint ventures	455,445	986,460
Tianjin Zerust [Member]
Net sales		3,735,457
Gross profit		1,783,673
Net income		265,648
Northern Technologies International Corporation’s share of equity in income of joint ventures		132,824
Net sales	42,000,424	52,178,238
Gross profit	18,523,102	25,540,546
Net income	3,872,728	6,152,182
Northern Technologies International Corporation’s share of equity in income of joint ventures	$ 1,936,420	$ 3,081,332