Note 6 - Investments in Joint Ventures - Condensed Balance Sheet of EXCOR and All Other Joint Ventures (Details) - USD ($)	May 31, 2019	Aug. 31, 2018
Current assets	$ 60,397,874	$ 58,086,747
Total assets	64,887,307	62,803,261
Current liabilities	15,628,449	15,991,886
Noncurrent liabilities	467,330	403,653
Joint ventures’ equity	48,791,528	46,407,722
NTIC’s share of joint ventures’ equity	24,077,361	22,950,995
NTIC’s share of joint ventures’ undistributed earnings	22,048,149	20,921,783
EXCOR [Member]
Current assets	29,698,867	27,354,788
Total assets	32,137,535	30,033,750
Current liabilities	4,606,287	4,535,954
Noncurrent liabilities
Joint ventures’ equity	27,531,248	25,497,796
NTIC’s share of joint ventures’ equity	13,765,626	12,748,899
NTIC’s share of joint ventures’ undistributed earnings	13,734,721	12,717,994
All Other [Member]
Current assets	30,699,007	30,731,959
Total assets	32,749,772	32,769,511
Current liabilities	11,022,162	11,455,932
Noncurrent liabilities	467,330	403,653
Joint ventures’ equity	21,260,280	20,909,926
NTIC’s share of joint ventures’ equity	10,311,735	10,195,263
NTIC’s share of joint ventures’ undistributed earnings	$ 8,313,428	$ 8,203,789