Note 7 - Investments in Joint Ventures (Tables)

12 Months Ended

Aug. 31, 2013

Equity Method Investments and Joint Ventures [Abstract]

Condensed Balance Sheet [Table Text Block]

	August 31, 2013
	TOTAL		EXCOR		China		All Other
Current assets	$	63,052,410	$	25,955,136	$	11,200,355	$	25,896,919
Total assets		68,417,142		28,391,787		11,226,755		28,798,600
Current liabilities		16,107,597		3,572,004		3,080,118		9,455,475
Noncurrent liabilities		2,488,057		—		871,886		1,616,171
Joint ventures’ equity		49,821,488		24,819,783		7,274,751		17,726,954
Northern Technologies International Corporation’s share of joint ventures’ equity		24,702,981		12,409,893		3,637,375		8,655,713
Northern Technologies International Corporation's share of joint ventures' undistributed earnings	$	22,281,510	$	12,378,988	$	3,587,375	$	6,315,147

	August 31, 2012
	TOTAL		EXCOR		NTI ASEAN		All Other
Current assets	$	61,973,725	$	24,357,139	$	15,358,967	$	22,257,619
Total assets		68,585,974		26,620,589		15,522,456		26,442,929
Current liabilities		18,686,181		4,749,574		5,763,857		8,172,750
Noncurrent liabilities		4,700,458		—		1,055,965		3,644,493
Joint ventures’ equity		45,199,335		21,871,015		8,702,634		14,625,686
Northern Technologies International Corporation’s share of joint ventures’ equity		21,461,492		10,935,509		3,685,404		6,840,579
Northern Technologies International Corporation's share of joint  ventures' undistributed earnings	$	19,403,150	$	10,904,604	$	3,314,445	$	5,184,101

Condensed Income Statement [Table Text Block]

	Fiscal Year Ended August 31, 2013
	TOTAL		EXCOR		China		All Other
Net sales	$	113,189,068	$	36,476,544	$	15,161,289	$	61,551,235
Gross profit		52,058,609		19,470,322		7,153,395		25,434,891
Net income		10,650,542		7,009,897		1,157,995		2,482,650
Northern Technologies International Corporation’s share of equity in income of joint ventures	$	5,237,711	$	3,507,057	$	579,376	$	1,151,278

	Fiscal Year Ended August 31, 2012
	TOTAL		EXCOR		NTI ASEAN		All Other
Net sales	$	111,830,961	$	36,027,979	$	22,035,035	$	53,767,947
Gross profit		50,679,875		18,667,848		9,621,930		22,390,097
Net income		11,987,323		6,656,298		3,585,476		1,745,549
Northern Technologies International Corporation’s share of equity in income of joint ventures	$	5,519,795	$	3,318,213	$	1,414,248	$	787,333