SHARE-BASED PAYMENT - Compensation Costs (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Compensation costs
Share-based compensation	$ 23,959	$ 21,134	$ 18,477
Excess tax benefit recognized	6,848	9,545	631
Restricted shares
Compensation costs
Share-based compensation	14,741	12,336	10,272
Stock options
Compensation costs
Share-based compensation	1,124	1,570	1,768
2014 PSP | RSUs
Compensation costs
Share-based compensation		766	3,625
2016 PSP | RSUs
Compensation costs
Share-based compensation	3,411	4,728	$ 2,812
2017 PSP | RSUs
Compensation costs
Share-based compensation	4,270	$ 1,734
2018 PSP | RSUs
Compensation costs
Share-based compensation	$ 413