Note 7 - Investments in Joint Ventures - Condensed Balance Sheet of EXCOR and All Other Joint Ventures (Details) - USD ($)		Nov. 30, 2021	Aug. 31, 2021
Current assets		$ 37,265,090	$ 33,747,089
Total assets		83,244,745	74,370,879
Current liabilities		11,389,728	8,516,196
Noncurrent liabilities		2,224,173	104,102
Joint ventures’ equity		66,292,224	62,368,026
Investments in joint ventures		21,357,911	27,623,768
Equity Method Investment, Nonconsolidated Investee or Group of Investees [Member]
Current assets		54,945,793	69,394,796
Total assets		58,833,491	73,814,402
Current liabilities		14,079,093	16,366,398
Noncurrent liabilities		1,288,670	1,455,524
Joint ventures’ equity		43,465,728	55,992,480
Investments in joint ventures		21,357,911	27,623,768
Northern Technologies International Corporation’s share of joint ventures’ undistributed earnings		19,142,941	24,702,778
EXCOR [Member]
Current assets		25,127,390	33,886,655
Total assets		27,282,965	36,211,520
Current liabilities		4,139,822	5,386,377
Noncurrent liabilities		0	0
Joint ventures’ equity		23,143,143	30,825,144
Investments in joint ventures		11,571,573	15,412,574
Northern Technologies International Corporation’s share of joint ventures’ undistributed earnings		11,540,668	14,697,490
All Other [Member]
Current assets		29,818,403
Total assets		31,550,526
Current liabilities		9,939,271
Noncurrent liabilities		1,288,670
Joint ventures’ equity		20,322,585
Investments in joint ventures		9,786,338
Northern Technologies International Corporation’s share of joint ventures’ undistributed earnings		$ 7,602,273
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.