Note 5 - Fair Value Measurements - Fair Value by Major Security Type (Details) - USD ($)	Sep. 30, 2019	Sep. 30, 2018
Short-term marketable securities	$ 3,695,364	$ 3,592,175
Long-term Securities	1,384,819	1,200,541
Fair Value, Nonrecurring [Member]
Cost Basis	5,344,359	5,212,054
Unrealized Gains (Losses)	11,362	(8,945)
Fair Value	5,355,721	5,203,109
Cash Equivalents	275,538	410,393
Short-term marketable securities	3,695,364	3,592,175
Long-term Securities	1,384,819	1,200,541
Fair Value, Nonrecurring [Member] | Fair Value, Inputs, Level 1 [Member]
Cost Basis	275,538	410,393
Unrealized Gains (Losses)
Fair Value	275,538	410,393
Cash Equivalents	275,538	410,393
Short-term marketable securities
Long-term Securities
Fair Value, Nonrecurring [Member] | Fair Value, Inputs, Level 2 [Member]
Cost Basis	5,068,821	4,801,661
Unrealized Gains (Losses)	11,362	(8,945)
Fair Value	5,080,183	4,792,716
Cash Equivalents
Short-term marketable securities	3,695,364	3,592,175
Long-term Securities	1,384,819	1,200,541
Fair Value, Nonrecurring [Member] | Fair Value, Inputs, Level 2 [Member] | Certificates of Deposit [Member]
Cost Basis	971,592	499,000
Unrealized Gains (Losses)
Fair Value	971,592	499,000
Cash Equivalents
Short-term marketable securities	499,000
Long-term Securities	472,592	499,000
Fair Value, Nonrecurring [Member] | Fair Value, Inputs, Level 2 [Member] | US States and Political Subdivisions Debt Securities [Member]
Cost Basis	240,463
Unrealized Gains (Losses)	205
Fair Value	240,668
Cash Equivalents
Short-term marketable securities	80,336
Long-term Securities	160,332
Fair Value, Nonrecurring [Member] | Fair Value, Inputs, Level 2 [Member] | Corporate Debt Securities [Member]
Cost Basis	3,856,766	4,302,661
Unrealized Gains (Losses)	11,157	(8,945)
Fair Value	3,867,923	4,293,716
Cash Equivalents
Short-term marketable securities	3,116,028	3,592,175
Long-term Securities	$ 751,895	$ 701,541