FAIR VALUE OF ASSETS AND LIABILITIES - Carrying Values and Estimated Fair Values of Financial Assets and Liabilities Measured on a Recurring Basis (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Sep. 30, 2017
Liabilities
Contingent consideration liability	$ 889	$ 311
Fair Value, Measurements, Nonrecurring | Carrying Value
Assets
Receivables from broker-dealers and clearing organizations	2,709	2,850
Forgivable loans receivable	1,598	1,616
Other Receivables, net	6,033	5,180
Total assets, excluding financial instruments	38,387	34,195
Liabilities
Accrued commissions and payroll payable	10,652	10,065
Accounts payable and accrued expenses	7,564	8,404
Total liabilities, excluding financial instruments	18,216	18,469
Fair Value, Measurements, Nonrecurring | Total Estimated Fair Value
Assets
Receivables from broker-dealers and clearing organizations	2,709	2,850
Forgivable loans receivable	1,598	1,616
Other Receivables, net	6,033	5,180
Total assets, excluding financial instruments	38,387	34,195
Liabilities
Accrued commissions and payroll payable	10,652	10,065
Accounts payable and accrued expenses	7,564	8,404
Total liabilities, excluding financial instruments	18,216	18,469
Fair Value, Measurements, Nonrecurring | Total Estimated Fair Value | Level 1
Assets
Receivables from broker-dealers and clearing organizations	0	0
Forgivable loans receivable	0	0
Other Receivables, net	0	0
Total assets, excluding financial instruments	28,047	24,549
Liabilities
Accrued commissions and payroll payable	0	0
Accounts payable and accrued expenses	0	0
Total liabilities, excluding financial instruments	0	0
Fair Value, Measurements, Nonrecurring | Total Estimated Fair Value | Level 2
Assets
Receivables from broker-dealers and clearing organizations	2,709	2,850
Forgivable loans receivable	1,598	1,616
Other Receivables, net	6,033	5,180
Total assets, excluding financial instruments	10,340	9,646
Liabilities
Accrued commissions and payroll payable	10,652	10,065
Accounts payable and accrued expenses	7,564	8,404
Total liabilities, excluding financial instruments	18,216	18,469
Cash | Fair Value, Measurements, Nonrecurring | Carrying Value
Assets
Cash and cash equivalents	27,211	23,508
Cash | Fair Value, Measurements, Nonrecurring | Total Estimated Fair Value
Assets
Cash and cash equivalents	27,211	23,508
Cash | Fair Value, Measurements, Nonrecurring | Total Estimated Fair Value | Level 1
Assets
Cash and cash equivalents	27,211	23,508
Cash | Fair Value, Measurements, Nonrecurring | Total Estimated Fair Value | Level 2
Assets
Cash and cash equivalents	0	0
Cash deposits with clearing organizations | Fair Value, Measurements, Nonrecurring | Carrying Value
Assets
Cash and cash equivalents	836	1,041
Cash deposits with clearing organizations | Fair Value, Measurements, Nonrecurring | Total Estimated Fair Value
Assets
Cash and cash equivalents	836	1,041
Cash deposits with clearing organizations | Fair Value, Measurements, Nonrecurring | Total Estimated Fair Value | Level 1
Assets
Cash and cash equivalents	836	1,041
Cash deposits with clearing organizations | Fair Value, Measurements, Nonrecurring | Total Estimated Fair Value | Level 2
Assets
Cash and cash equivalents	$ 0	$ 0