PER SHARE RESULTS - Basic net income per share (Details) - shares	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
PER SHARE RESULTS
Weighted average shares used for basic net income per share	18,013,863	19,318,358	18,134,607	19,317,029
Effect of dilutive stock options	16,273	41,134	23,385	43,010
Weighted average shares used for diluted net income per share	18,030,136	19,359,492	18,157,992	19,360,039