ACCOUNTS RECEIVABLE AND RELATED ALLOWANCE FOR DOUBTFUL ACCOUNTS AND SALES RESERVES (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Accounts Receivable
Accounts receivable	$ 295,013	$ 396,427
Allowance for doubtful accounts and sales reserves	(18,911)	(17,515)
Accounts receivable, net of allowance for doubtful accounts and sales reserves	276,102	378,912
Allowance for Doubtful Accounts
Balance At Beginning Of Year	8,265	9,419	$ 3,885
Additions Charged To Costs And Expenses	16,349	4,549	8,909
Deductions From Reserves	(10,156)	(5,703)	(3,375)
Balance At End Of Year	14,458	8,265	9,419
Allowance for Sales Reserves
Balance At Beginning Of Year	9,250	7,271	390
Additions Charged To Revenues	8,768	11,394	14,254
Deductions From Reserves	(13,566)	(9,415)	(7,373)
Balance At End Of Year	$ 4,452	$ 9,250	$ 7,271