ACQUISITIONS (Details) - FBR & Co. ("FBR") [Member] $ / shares in Units, $ in Thousands	Jun. 01, 2017 USD ($) $ / shares shares
Consideration paid by B. Riley:
Number of FBR Common Shares outstanding at June 1, 2017	7,099,511
Stock merger exchange ratio	0.671
Number of B. Riley common shares	4,763,772
Number of B. Riley common shares to be issued from acceleration of vesting for outstanding FBR stock options, restricted stock and RSU awards	67,861
Total number of B. Riley common shares to be issued	4,831,633
Closing market price of B. Riley common shares on December 31, 2016 | $ / shares	$ 14.70
Total value of B. Riley common shares | $	$ 71,025
Fair value of RSU's attributable to service period prior to June 1, 2017 | $	2,446	[1]
Total consideration | $	$ 73,471

[1] Outstanding FBR restricted stock awards at June 1, 2017, the date of the acquisition, were adjusted in accordance with the Merger Agreement with the right to receive 0.671 shares of the Company's common stock for each outstanding FBR stock award unit. The fair value of the FBR restricted stock awards at June 1, 2017 was determined based on the closing price of the Company's common stock of $14.70 on June 1, 2017. The fair value of the FBR restricted stock awards were apportioned as purchase consideration based on service provided to FBR as of June 1, 2017 with the remaining fair value of the FBR restricted stock awards to be recognized prospectively over the restricted stock and FBR restricted stock awards remaining vesting period.