SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Details 3) - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016
Securities and other investments owned:
Total assets measured at fair value	$ 78,204	$ 16,579
Securities sold not yet purchased
Securities sold not yet purchased	3,526	846
Contingent consideration		1,242
Common Stock [Member]
Securities sold not yet purchased
Securities sold not yet purchased	2,594
Corporate Bonds [Member]
Securities and other investments owned:
Total assets measured at fair value	1,620	1,025
Securities sold not yet purchased
Securities sold not yet purchased	932	846
Partnership Interests [Member]
Securities and other investments owned:
Total assets measured at fair value	26,705	13,470
Common Stocks and Warrants [Member]
Securities and other investments owned:
Total assets measured at fair value	20,771	2,084
Loans Receivable [Member]
Securities and other investments owned:
Total assets measured at fair value	29,108
Fair Value, Measurements, Recurring [Member]
Securities and other investments owned:
Total assets measured at fair value	73,225	16,579
Securities sold not yet purchased
Securities sold not yet purchased	3,526
Mandatorily redeemable noncontrolling interests issued after November 5, 2003	9,641	3,214
Contingent consideration		1,242
Total liabilities measured at fair value	13,167	5,302
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member]
Securities and other investments owned:
Total assets measured at fair value	15,668	1,785
Securities sold not yet purchased
Securities sold not yet purchased	2,594
Mandatorily redeemable noncontrolling interests issued after November 5, 2003
Contingent consideration
Total liabilities measured at fair value	2,594
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member]
Securities and other investments owned:
Total assets measured at fair value	1,664	909
Securities sold not yet purchased
Securities sold not yet purchased	932
Mandatorily redeemable noncontrolling interests issued after November 5, 2003
Contingent consideration
Total liabilities measured at fair value	932	846
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member]
Securities and other investments owned:
Total assets measured at fair value	55,893	13,885
Securities sold not yet purchased
Securities sold not yet purchased
Mandatorily redeemable noncontrolling interests issued after November 5, 2003	9,641	3,214
Contingent consideration		1,242
Total liabilities measured at fair value	9,641	4,456
Fair Value, Measurements, Recurring [Member] | Common Stock [Member]
Securities and other investments owned:
Total assets measured at fair value		2,084
Securities sold not yet purchased
Securities sold not yet purchased	2,594
Fair Value, Measurements, Recurring [Member] | Common Stock [Member] | Fair Value, Inputs, Level 1 [Member]
Securities and other investments owned:
Total assets measured at fair value		1,785
Securities sold not yet purchased
Securities sold not yet purchased	2,594
Fair Value, Measurements, Recurring [Member] | Common Stock [Member] | Fair Value, Inputs, Level 2 [Member]
Securities and other investments owned:
Total assets measured at fair value
Securities sold not yet purchased
Securities sold not yet purchased
Fair Value, Measurements, Recurring [Member] | Common Stock [Member] | Fair Value, Inputs, Level 3 [Member]
Securities and other investments owned:
Total assets measured at fair value		299
Securities sold not yet purchased
Securities sold not yet purchased
Fair Value, Measurements, Recurring [Member] | Corporate Bonds [Member]
Securities and other investments owned:
Total assets measured at fair value	1,620	1,025
Securities sold not yet purchased
Securities sold not yet purchased	932	846
Fair Value, Measurements, Recurring [Member] | Corporate Bonds [Member] | Fair Value, Inputs, Level 1 [Member]
Securities and other investments owned:
Total assets measured at fair value
Securities sold not yet purchased
Securities sold not yet purchased
Fair Value, Measurements, Recurring [Member] | Corporate Bonds [Member] | Fair Value, Inputs, Level 2 [Member]
Securities and other investments owned:
Total assets measured at fair value	1,620	865
Securities sold not yet purchased
Securities sold not yet purchased	932	846
Fair Value, Measurements, Recurring [Member] | Corporate Bonds [Member] | Fair Value, Inputs, Level 3 [Member]
Securities and other investments owned:
Total assets measured at fair value		160
Securities sold not yet purchased
Securities sold not yet purchased
Fair Value, Measurements, Recurring [Member] | Partnership Interests [Member]
Securities and other investments owned:
Total assets measured at fair value	21,726	13,470
Fair Value, Measurements, Recurring [Member] | Partnership Interests [Member] | Fair Value, Inputs, Level 1 [Member]
Securities and other investments owned:
Total assets measured at fair value	4,660
Fair Value, Measurements, Recurring [Member] | Partnership Interests [Member] | Fair Value, Inputs, Level 2 [Member]
Securities and other investments owned:
Total assets measured at fair value	44	44
Fair Value, Measurements, Recurring [Member] | Partnership Interests [Member] | Fair Value, Inputs, Level 3 [Member]
Securities and other investments owned:
Total assets measured at fair value	17,022	$ 13,426
Fair Value, Measurements, Recurring [Member] | Common Stocks and Warrants [Member]
Securities and other investments owned:
Total assets measured at fair value	20,771
Fair Value, Measurements, Recurring [Member] | Common Stocks and Warrants [Member] | Fair Value, Inputs, Level 1 [Member]
Securities and other investments owned:
Total assets measured at fair value	11,008
Fair Value, Measurements, Recurring [Member] | Common Stocks and Warrants [Member] | Fair Value, Inputs, Level 2 [Member]
Securities and other investments owned:
Total assets measured at fair value
Fair Value, Measurements, Recurring [Member] | Common Stocks and Warrants [Member] | Fair Value, Inputs, Level 3 [Member]
Securities and other investments owned:
Total assets measured at fair value	9,763
Fair Value, Measurements, Recurring [Member] | Loans Receivable [Member]
Securities and other investments owned:
Total assets measured at fair value	29,108
Fair Value, Measurements, Recurring [Member] | Loans Receivable [Member] | Fair Value, Inputs, Level 1 [Member]
Securities and other investments owned:
Total assets measured at fair value
Fair Value, Measurements, Recurring [Member] | Loans Receivable [Member] | Fair Value, Inputs, Level 2 [Member]
Securities and other investments owned:
Total assets measured at fair value
Fair Value, Measurements, Recurring [Member] | Loans Receivable [Member] | Fair Value, Inputs, Level 3 [Member]
Securities and other investments owned:
Total assets measured at fair value	$ 29,108