EARNINGS PER SHARE (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended				6 Months Ended
	Jun. 30, 2019	Mar. 31, 2019	Jun. 30, 2018	Mar. 31, 2018	Jun. 30, 2019	Jun. 30, 2018
Basic EPS Calculation
Net income available for common stock	$ 24,470	$ 93,660	$ 20,419	$ 90,835	$ 118,130	$ 111,254
Weighted Average Number of Shares Outstanding, Basic	52,890		52,692		52,858	52,648
Earnings Per Share, Basic	$ 0.46		$ 0.39		$ 2.23	$ 2.11
Diluted EPS Calculation
Net income available for common stock	$ 24,470	$ 93,660	$ 20,419	$ 90,835	$ 118,130	$ 111,254
Effect of dilutive securities on income	$ 0		$ 0		$ 0	$ 0
Effect of dilutive securities on shares	325		207		352	250
Weighted Average Number of Shares Outstanding, Diluted	53,215		52,899		53,210	52,898
Earnings Per Share, Diluted	$ 0.46		$ 0.39		$ 2.22	$ 2.10