SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Earnings Per Share (Details) - $ / shares shares in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Shares
Basic (in shares)									18,025	17,846	17,585
Effect of dilutive stock options (in shares)									659	728	782
Diluted (in shares)									18,684	18,574	18,367
Per Share Amount
Basic (in dollars per share)	$ 0.34	$ 0.52	$ 0.52	$ 0.39	$ 0.40	$ 0.61	$ 0.52	$ 0.38	$ 1.77	$ 1.91	$ 1.45
Effect of dilutive stock options (in dollars per share)									(0.07)	(0.08)	(0.06)
Diluted (in dollars per share)	$ 0.33	$ 0.50	$ 0.50	$ 0.38	$ 0.39	$ 0.58	$ 0.50	$ 0.36	$ 1.70	$ 1.83	$ 1.39