STOCK AWARD PLANS - Total Compensation Expense Recognized (Details) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	$ 10,776,000	$ 8,850,000	$ 33,127,000	$ 40,657,000
Stock options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	5,081,000	4,829,000	15,119,000	13,539,000
Stock awards
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	5,042,000	3,470,000	15,736,000	24,798,000
Company expense on ESPP discount
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	$ 652,875	$ 551,000	$ 2,272,000	$ 2,320,000