Note 7 - Investments in Joint Ventures (Details) - Condensed Balance Sheet of EXCOR and NTI ASEAN, and All Other Joint Ventures (USD $)	Aug. 31, 2014	Aug. 31, 2013
Condensed Balance Sheet Statements, Captions [Line Items]
Current assets	$ 61,491,957	$ 63,052,410
Total assets	65,466,964	68,417,142
Current liabilities	17,542,634	16,107,597
Noncurrent liabilities	1,929,488	2,488,057
Joint ventures’ equity	45,994,842	49,821,488
Northern Technologies International Corporation’s share of joint ventures’ equity	22,961,989	24,702,981
Northern Technologies International Corporation's share of joint ventures’ undistributed earnings	20,540,523	22,281,510
EXCOR [Member]
Condensed Balance Sheet Statements, Captions [Line Items]
Current assets	24,361,157	25,955,136
Total assets	26,652,165	28,391,787
Current liabilities	3,512,143	3,572,004
Joint ventures’ equity	23,140,022	24,819,783
Northern Technologies International Corporation’s share of joint ventures’ equity	11,570,013	12,409,893
Northern Technologies International Corporation's share of joint ventures’ undistributed earnings	11,539,108	12,378,988
China [Member]
Condensed Balance Sheet Statements, Captions [Line Items]
Current assets	9,774,680	11,200,355
Total assets	9,793,803	11,226,755
Current liabilities	4,438,380	3,080,118
Noncurrent liabilities	868,377	871,886
Joint ventures’ equity	4,487,046	7,274,751
Northern Technologies International Corporation’s share of joint ventures’ equity	2,243,524	3,637,375
Northern Technologies International Corporation's share of joint ventures’ undistributed earnings	2,193,524	3,587,375
All Other [Member]
Condensed Balance Sheet Statements, Captions [Line Items]
Current assets	27,356,120	25,896,919
Total assets	29,020,996	28,798,600
Current liabilities	9,592,111	9,455,475
Noncurrent liabilities	1,061,111	1,616,171
Joint ventures’ equity	18,367,775	17,726,954
Northern Technologies International Corporation’s share of joint ventures’ equity	9,148,452	8,655,713
Northern Technologies International Corporation's share of joint ventures’ undistributed earnings	$ 6,807,891	$ 6,315,147