SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Weighted average number of common shares outstanding (Details) - shares	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES
Weighted average number of common shares used in computing basic net income per share	19,016,808	15,812,585	11,763,050
Effect of dilutive stock options	46,429	65,048	63,927
Weighted average shares used for diluted net income available to common shareholders	19,063,237	15,877,633	11,826,977