STOCK BASED COMPENSATION - Restricted Stock Awards (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended			12 Months Ended
	Mar. 31, 2017	Mar. 31, 2016	Mar. 31, 2015	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Additional disclosures
Compensation expense				$ 311	$ 382	$ 315
Restricted stock
Shares
Nonvested at the beginning of the period (in shares)	104,319			104,319
Granted (in shares)				30,302
Vested (in shares)				(29,432)
Forfeited (in shares)				(2,250)
Nonvested at the end of the period (in shares)				102,939	104,319
Weighted Average Grant Date Fair Value
Nonvested at the beginning of the period (in dollars per share)	$ 20.03			$ 20.03
Granted (in dollars per share)				34.38
Vested (in dollars per share)				16.37
Forfeited (in dollars per share)				22.65
Nonvested at the end of the period (in dollars per share)				$ 25.25	$ 20.03
Restricted stock | 2007 Stock Incentive Plan
Additional disclosures
Unrecognized compensation costs				$ 1,327
Weighted-average period of expected recognition of the cost				2 years 18 days
Compensation expense				$ 767	$ 670	$ 584
Restricted stock | Executive officer and other employees
Stock-based compensation
Vesting percentage of stock awards on third anniversary of grant date				100.00%
Shares
Granted (in shares)				30,302	50,152	28,955
Performance units | Executive officers
Shares
Granted (in shares)	11,302	16,152	16,205
Weighted Average Grant Date Fair Value
Granted (in dollars per share)	$ 35.04	$ 21.41	$ 19.57
Additional disclosures
Vesting period				3 years
Compensation expense				$ 241	$ 240	$ 79