SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Schedule of Earnings Per Share (Details) - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Accounting Policies [Abstract]
Net income available to common shareholders	$ 73,548	$ 72,100	$ 40,847
Weighted average number of common shares outstanding (in shares)	36,828	34,347	31,762
Effect of dilutive stock options (in shares)	62	108	121
Effect of dilutive restricted stock awards (in shares)	254	247	244
Weighted average number of common shares outstanding used to calculate diluted earnings per share (in shares)	37,144	34,702	32,127