CASH, CASH EQUIVALENTS AND RESTRICTED CASH - Narrative (Details) - USD ($) $ in Thousands	6 Months Ended
Jun. 30, 2020	May 31, 2020	Dec. 31, 2019
Cash and Cash Equivalents [Abstract]
Proceeds from sale of debt securities, available-for-sale	$ 253,400
Marketable securities proceeds reinvested	73,000
Restricted cash	$ 910		$ 22,037
Letters of credit outstanding		$ 21,500

Amount of cash and cash equivalents restricted as to withdrawal or usage, classified as noncurrent. Cash includes, but is not limited to, currency on hand, demand deposits with banks or financial institutions, and other accounts with general characteristics of demand deposits. Cash equivalents include, but are not limited to, short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates.

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Name:	us-gaap_RestrictedCashAndCashEquivalentsNoncurrent
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant