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STOCK-BASED COMPENSATION (Narrative) (Details) - USD ($)	1 Months Ended	12 Months Ended			144 Months Ended	192 Months Ended
	May 31, 2014	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2020	Dec. 31, 2020	May 20, 2020	May 19, 2020	Dec. 31, 2008	Dec. 31, 2004
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Additional shares authorized (in shares)		150,000				150,000
Allocated share-based compensation expense		$ 4,991,000	$ 6,152,000	$ 5,249,000
Stock-based compensation expense		4,095,000			$ 4,095,000	$ 4,095,000
Intrinsic value of options exercised		299,000	2,055,000	5,850,000
Restricted Stock Awards
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Allocated share-based compensation expense		3,734,000	4,659,000	$ 3,877,000
Total compensation expense that has yet to be recognized		3,074,000			3,074,000	3,074,000
Intrinsic value of the unvested restricted stock awards outstanding		$ 5,469,000	$ 10,165,000		$ 5,469,000	$ 5,469,000
Employee Stock Award Plan-2008
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of authorized shares available for future issuance (in shares)		700,680	834,910		700,680	700,680			1,900,000
Additional shares authorized (in shares)	1,500,000	0			1,500,000
Award expiration term		10 years
Employee Stock Award Plan-2008 \| Restricted Stock Awards \| Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period of restricted stock awards		3 years
Employee Stock Award Plan-2008 \| Restricted Stock Awards \| Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period of restricted stock awards		5 years
Employee Stock Award Plan-2008 \| Tranche one
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percentage of option awards vest and exercisable in installments		20.00%
Employee Stock Award Plan-2008 \| Tranche two
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Percentage of option awards vest and exercisable in installments		33.30%
Director Plan - 2005
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of authorized shares available for future issuance (in shares)		160,135	34,863		160,135	160,135	450,000	300,000		300,000