Note 5 - Fair Value Measurements - Fair Value by Major Security Type (Details) - USD ($)	Dec. 31, 2018	Sep. 30, 2018
Short-term marketable securities	$ 3,783,863	$ 3,592,175
Long-term Securities	899,759	1,200,541
Fair Value, Measurements, Nonrecurring [Member]
Cost Basis	5,232,032	5,212,054
Unrealized Gains (Losses)	(9,557)	(8,945)
Fair Value	5,222,475	5,203,109
Cash Equivalents	538,853	410,393
Short-term marketable securities	3,783,863	3,592,175
Long-term Securities	899,759	1,200,541
Fair Value, Measurements, Nonrecurring [Member] | Fair Value, Inputs, Level 1 [Member]
Cost Basis	538,922	410,393
Unrealized Gains (Losses)	(69)
Fair Value	538,853	410,393
Cash Equivalents	538,853	410,393
Short-term marketable securities
Long-term Securities
Fair Value, Measurements, Nonrecurring [Member] | Fair Value, Inputs, Level 2 [Member]
Cost Basis	4,693,110	4,801,661
Unrealized Gains (Losses)	(9,488)	(8,945)
Fair Value	4,683,622	4,792,716
Cash Equivalents
Short-term marketable securities	3,783,863	3,592,175
Long-term Securities	899,759	1,200,541
Fair Value, Measurements, Nonrecurring [Member] | Fair Value, Inputs, Level 2 [Member] | Certificates of Deposit [Member]
Cost Basis	499,000	499,000
Unrealized Gains (Losses)
Fair Value	499,000	499,000
Cash Equivalents
Short-term marketable securities
Long-term Securities	499,000	499,000
Fair Value, Measurements, Nonrecurring [Member] | Fair Value, Inputs, Level 2 [Member] | US States and Political Subdivisions Debt Securities [Member]
Cost Basis	286,070
Unrealized Gains (Losses)	(277)
Fair Value	285,793
Cash Equivalents
Short-term marketable securities	285,793
Long-term Securities
Fair Value, Measurements, Nonrecurring [Member] | Fair Value, Inputs, Level 2 [Member] | Corporate Debt Securities [Member]
Cost Basis	3,908,040	4,302,661
Unrealized Gains (Losses)	(9,211)	(8,945)
Fair Value	3,898,829	4,293,716
Cash Equivalents
Short-term marketable securities	3,498,070	3,592,175
Long-term Securities	$ 400,759	$ 701,541