AQUISITIONS (Details 1) - USD ($)
$ / shares in Units, $ in Thousands
3 Months Ended 12 Months Ended
Dec. 31, 2016
Sep. 30, 2016
Jun. 30, 2016
Mar. 31, 2016
Dec. 31, 2015
Sep. 30, 2015
Jun. 30, 2015
Mar. 31, 2015
Dec. 31, 2016
Dec. 31, 2015
Dec. 31, 2014
Weighted average basic shares outstanding (in shares) 19,004,548 18,977,072 17,935,254 16,490,178 16,283,677 16,243,425 16,237,860 16,117,422 18,106,621 16,221,040 9,612,154
Weighted average diluted shares outstanding (in shares) 19,511,292 19,208,527 17,935,254 16,553,953 16,283,677 16,344,649 16,310,829 16,162,304 18,391,852 16,265,915 9,612,154
United Online Inc [Member]                      
Revenues                 $ 226,806 $ 202,752  
Net income attributable to B. Riley Financial, Inc.                 $ 13,288 $ 9,347  
Basic earnings per share (in dollars per share)                 $ 0.73 $ 0.58  
Diluted earnings per share (in dollars per share)                 $ 0.72 $ 0.57  
Weighted average basic shares outstanding (in shares)                 18,106,621 16,221,040  
Weighted average diluted shares outstanding (in shares)                 18,391,852 16,265,915