Note 6 - Condensed Income Statement of EXCOR, Tianjin Zerust, and All Other Joint Ventures (Details) - USD ($)	3 Months Ended
	Nov. 30, 2015	Nov. 30, 2014
EXCOR [Member]
Net sales	$ 8,207,696	$ 9,524,270
Gross profit	4,153,477	4,974,751
Net income	1,536,247	1,956,191
Northern Technologies International Corporation’s share of equity in income of joint ventures	768,123	978,096
All Other [Member]
Net sales	13,663,513	15,861,125
Gross profit	5,494,604	7,277,360
Net income	425,675	962,731
Northern Technologies International Corporation’s share of equity in income of joint ventures	215,630	495,763
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	21,871,209	29,120,852
Gross profit	9,648,081	14,035,784
Net income	1,961,922	3,184,570
Northern Technologies International Corporation’s share of equity in income of joint ventures	$ 983,753	$ 1,606,683