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	Dec. 31, 2018	Sep. 30, 2018
Liabilities
Contingent consideration liability	$ 705	$ 744
Fair Value, Measurements, Nonrecurring | Carrying Value
Assets
Receivables from broker-dealers and clearing organizations	2,751	3,967
Forgivable loans receivable	1,531	1,567
Other Receivables, net	5,595	4,265
Total assets, excluding financial instruments	41,026	38,055
Liabilities
Accrued commissions and payroll payable	13,040	12,862
Accounts payable and accrued expenses	7,402	7,275
Total liabilities, excluding financial instruments	20,442	20,137
Fair Value, Measurements, Nonrecurring | Total Estimated Fair Value
Assets
Receivables from broker-dealers and clearing organizations	2,751	3,967
Forgivable loans receivable	1,531	1,567
Other Receivables, net	5,595	4,265
Total assets, excluding financial instruments	41,026	38,055
Liabilities
Accrued commissions and payroll payable	13,040	12,862
Accounts payable and accrued expenses	7,402	7,275
Total liabilities, excluding financial instruments	20,442	20,137
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	31,149	28,256
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	2,751	3,967
Forgivable loans receivable	1,531	1,567
Other Receivables, net	5,595	4,265
Total assets, excluding financial instruments	9,877	9,799
Liabilities
Accrued commissions and payroll payable	13,040	12,862
Accounts payable and accrued expenses	7,402	7,275
Total liabilities, excluding financial instruments	20,442	20,137
Cash | Fair Value, Measurements, Nonrecurring | Carrying Value
Assets
Cash and cash equivalents	30,813	27,920
Cash | Fair Value, Measurements, Nonrecurring | Total Estimated Fair Value
Assets
Cash and cash equivalents	30,813	27,920
Cash | Fair Value, Measurements, Nonrecurring | Total Estimated Fair Value | Level 1
Assets
Cash and cash equivalents	30,813	27,920
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	336	336
Cash deposits with clearing organizations | Fair Value, Measurements, Nonrecurring | Total Estimated Fair Value
Assets
Cash and cash equivalents	336	336
Cash deposits with clearing organizations | Fair Value, Measurements, Nonrecurring | Total Estimated Fair Value | Level 1
Assets
Cash and cash equivalents	336	336
Cash deposits with clearing organizations | Fair Value, Measurements, Nonrecurring | Total Estimated Fair Value | Level 2
Assets
Cash and cash equivalents	$ 0	$ 0