FAIR VALUE MEASUREMENTS (Details)	3 Months Ended		9 Months Ended
	Sep. 30, 2022 USD ($) $ / shares	Sep. 30, 2021 USD ($)	Sep. 30, 2022 USD ($) $ / shares	Sep. 30, 2021 USD ($)	Dec. 31, 2021 USD ($)	Feb. 28, 2019 USD ($)	May 31, 2018 USD ($)
Investments in securities:
Investments in trading securities	$ 51,564,000		$ 51,564,000		$ 65,024,000
Total assets measured at fair value	55,565,000		55,565,000		69,537,000
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	4,024,000	$ 4,087,000	4,369,000	$ 3,431,000
Unrealized gains (losses) on private investments	(248,000)	(13,000)	(593,000)	643,000
Ending balance	$ 3,776,000	$ 4,074,000	$ 3,776,000	$ 4,074,000
Fair Value Inputs [Abstract] (Deprecated 2018-01-31)
Unobservable input -book value multiple - minimum | $ / shares	1.47		1.47
Unobservable input -book value multiple - maximum	1.99		1.99
Unobservable input -book value multiple - weighted average	1.66		1.66
Long-term Investments	$ 4,455,000		$ 4,455,000		4,455,000	$ 300,000	$ 5,400,000
Level 1
Investments in securities:
Investments in trading securities	51,564,000		51,564,000		65,024,000
Total assets measured at fair value	51,564,000		51,564,000		65,024,000
Level 2
Investments in securities:
Investments in trading securities	0		0		0
Total assets measured at fair value	0		0		0
Level 3
Investments in securities:
Investments in trading securities	0		0		0
Total assets measured at fair value	3,776,000		3,776,000		4,369,000
Investments Measured at NAV
Investments in securities:
Investments in trading securities	0		0		0
Total assets measured at fair value	225,000		225,000		144,000
Private investment fund
Investments in securities:
Private	225,000		225,000		144,000
Private investment fund | Level 1
Investments in securities:
Private	0		0		0
Private investment fund | Level 2
Investments in securities:
Private	0		0		0
Private investment fund | Level 3
Investments in securities:
Private	0		0		0
Private investment fund | Investments Measured at NAV
Investments in securities:
Private	225,000		225,000		144,000
Private equity
Investments in securities:
Private	3,776,000		3,776,000		4,369,000
Private equity | Level 1
Investments in securities:
Private	0		0		0
Private equity | Level 2
Investments in securities:
Private	0		0		0
Private equity | Level 3
Investments in securities:
Private	3,776,000		3,776,000		4,369,000
Private equity | Investments Measured at NAV
Investments in securities:
Private	$ 0		$ 0		$ 0