Net Capital Requirements (Details) $ in Thousands	Sep. 30, 2020 USD ($)
B. Riley Securities [Member]
Net Capital Requirements (Details) [Line Items]
Net capital	$ 137,777
Excess capital	134,273
B. Riley Securities [Member] | Maximum [Member]
Net Capital Requirements (Details) [Line Items]
Excess capital	3,504
B. Riley Wealth Management [Member]
Net Capital Requirements (Details) [Line Items]
Net capital	4,090
Excess capital	3,444
B. Riley Wealth Management [Member] | Maximum [Member]
Net Capital Requirements (Details) [Line Items]
Excess capital	$ 646