EARNINGS PER SHARE (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Basic EPS Calculation
Net income available for common stock	$ 16,276	$ 18,797	$ 127,530	$ 115,876
Weighted Average Number of Shares Outstanding, Basic	52,736	52,488	52,678	52,539
Earnings Per Share, Basic	$ 0.31	$ 0.36	$ 2.42	$ 2.21
Diluted EPS Calculation
Net income available for common stock	$ 16,276	$ 18,797	$ 127,530	$ 115,876
Effect of dilutive securities on income	$ 0	$ 0	$ 0	$ 0
Effect of dilutive securities on shares	376	438	291	445
Weighted Average Number of Shares Outstanding, Diluted	53,112	52,926	52,969	52,984
Earnings Per Share, Diluted	$ 0.31	$ 0.36	$ 2.41	$ 2.19