SHAREHOLDERS' EQUITY (Details) - Common Stock - shares	3 Months Ended	12 Months Ended
	Mar. 31, 2019	Dec. 31, 2018	Feb. 28, 2015
Shareholder's Equity
Common stock, shares authorized to be repurchased			20,000,000
Remaining shares authorized to be repurchased	8,004,726
Reacquired shares	766,648	3,908,041
Number of shares reacquired through the open market or private purchases	646,668	3,706,716
Number of shares that have been repurchased through the exercise of stock options and vesting of stock awards	119,980	201,325