Note 7 - Investments in Joint Ventures - Condensed Balance Sheet of EXCOR and All Other Joint Ventures (Details) - USD ($)		Feb. 28, 2022	Aug. 31, 2021
Current assets		$ 38,597,623	$ 33,747,089
Total assets		84,950,651	74,370,879
Current liabilities		13,271,186	8,516,196
Noncurrent liabilities		2,241,698	104,102
Joint ventures’ equity		66,065,839	62,368,026
Investments in joint ventures		21,852,070	27,623,768
Equity Method Investment, Nonconsolidated Investee or Group of Investees [Member]
Current assets		55,032,109	69,394,796
Total assets		58,525,731	73,814,402
Current liabilities		12,803,351	16,366,398
Noncurrent liabilities		1,268,334	1,455,524
Joint ventures’ equity		44,454,046	55,992,480
Investments in joint ventures		21,852,070	27,623,768
Northern Technologies International Corporation’s share of joint ventures’ undistributed earnings		20,501,921	24,702,778
EXCOR [Member]
Current assets		25,447,104	33,886,655
Total assets		27,186,903	36,211,520
Current liabilities		3,004,495	5,386,377
Noncurrent liabilities		0	0
Joint ventures’ equity		24,182,408	30,825,144
Investments in joint ventures		12,091,206	15,412,574
Northern Technologies International Corporation’s share of joint ventures’ undistributed earnings		12,060,301	14,697,490
All Other [Member]
Current assets		29,585,005
Total assets		31,338,828
Current liabilities		9,798,856
Noncurrent liabilities		1,268,334
Joint ventures’ equity		20,271,638
Investments in joint ventures		9,760,864
Northern Technologies International Corporation’s share of joint ventures’ undistributed earnings		$ 8,441,621
Joint Ventures in France [Member]
Current assets	[1]		35,508,141
Total assets	[1]		37,602,882
Current liabilities	[1]		10,980,021
Noncurrent liabilities	[1]		1,455,524
Joint ventures’ equity	[1]		25,167,336
Investments in joint ventures	[1]		12,211,194
Northern Technologies International Corporation’s share of joint ventures’ undistributed earnings	[1]		$ 10,005,288

[1] Includes Harita-NTI since Harita-NTI was not a consolidated subsidiary of the Company as of Augut 31, 2021 or November 30, 2020. See Note 3.