STOCKHOLDERS' EQUITY - Restricted stock grants (Details) - Restricted stock awards [Member] - $ / shares	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
STOCKHOLDERS' EQUITY
Shares, Unvested at beginning of year	1,814,000	2,124,000
Shares, Grants	1,649,000	2,604,000
Shares, Vested	(1,739,000)	(2,840,000)
Shares, Forfeited/cancelled/expired		(74,000)
Shares, Unvested at end of year	1,724,000	1,814,000
Average Fair Value at Grant Date, Unvested at beginning of year (in dollars per share)	$ 2.14	$ 1.85
Average Fair Value at Grant Date, Grants (in dollars per share)	0.77	2.16
Average Fair Value at Grant Date, Vested (in dollars per share)	2.14	1.94
Average Fair Value at Grant Date, Forfeited/cancelled/expired (in dollars per share)		2.19
Average Fair Value at Grant Date, Unvested at end of year (in dollars per share)	$ 0.83	$ 2.14