SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Weighted Average Shares Outstanding (Details) - shares shares in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Accounting Policies [Abstract]
Weighted average number of shares outstanding – basic	33,704	33,198	33,018
Effect of dilutive securities:
Stock options	281	162	0
Non-vested stock and stock units	319	381	0
Weighted average number of shares outstanding – diluted	34,304	33,741	33,018
Anti-dilutive securities	271	221	922