SHAREHOLDERS' EQUITY - Stock Purchase Plan (Details) - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Non-cash compensation expense recognized	$ 9,255	$ 16,184	$ 15,149
ESPP
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares purchased (in shares)	166	335	228
Non-cash compensation expense recognized	$ 43	$ 234	$ 252

Number of shares issued during the period as a result of an employee stock purchase plan.

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration