CALCULATION OF EARNINGS PER COMMON SHARE (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended												12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Earnings Per Share [Abstract]
NET INCOME AVAILABLE TO COMMON SHAREHOLDERS													$ 136,515	$ 60,776	$ 85,385
Weighted average number of common shares outstanding
Basic weighted average shares outstanding (in shares)													32,784,724	32,888,007	33,820,148
Diluted weighted shares outstanding (in shares)													32,894,425	32,986,707	33,853,511
Earnings per common share
Basic (in dollars per share)	$ 1.10	$ 1.17	$ 1.01	$ 0.89	$ (0.41)	$ 0.76	$ 0.77	$ 0.72	$ 0.69	$ 0.70	$ 0.62	$ 0.52	$ 4.16	$ 1.85	$ 2.52
Diluted (in dollars per share)	$ 1.09	$ 1.17	$ 1.00	$ 0.89	$ (0.41)	$ 0.76	$ 0.77	$ 0.72	$ 0.69	$ 0.70	$ 0.61	$ 0.52	$ 4.15	$ 1.84	$ 2.52