STOCK-BASED COMPENSATION PLANS - Summary of Stock Options Activity (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Number of Stock Options Outstanding
Beginning balance (in shares)	236,763	344,159
Granted (in shares)	0	0
Exercised (in shares)	(55,725)	(85,085)
Forfeited (in shares)	(11,117)	(22,311)
Ending balance (in shares)	169,921	236,763
Ending vested and expected to vest (in shares)	169,921	234,709
Exercisable, outstanding (in shares)	100,317	90,807
Weighted Average Exercise Price
Beginning balance (usd per share)	$ 17.99	$ 17.56
Granted (usd per share)	0.00	0.00
Exercised (usd per share)	15.19	16.10
Forfeited (usd per share)	17.38	18.49
Ending balance (usd per share)	18.95	17.99
Ending vested and expected to vest (usd per share)	18.95	18.04
Exercisable (usd per share)	$ 18.66	$ 16.08
Aggregate Intrinsic Value
Value of ending outstanding balance	$ 1,370	$ 3,213
Ending vested and expected to vest	1,370	3,173
Exercisable, aggregate intrinsic value	$ 838	$ 1,406