SHARE-BASED COMPENSATION PLANS - Summary (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Share-based compensation expense and income tax benefits recognized during the periods
Share-based compensation expense	$ 29,993	$ 25,828	$ 24,952
Income tax benefit	(4,728)	(4,667)	(4,615)
Share-based compensation expense, net of tax	25,265	21,161	20,337
Unvested stock awards
Share-based compensation expense and income tax benefits recognized during the periods
Share-based compensation expense	25,509	19,253	17,249
Stock option and employee stock purchase plans
Share-based compensation expense and income tax benefits recognized during the periods
Share-based compensation expense	$ 4,484	$ 6,575	$ 7,703