RECEIVABLES, CONTRACT ASSETS, AND DEFERRED REVENUE - Summary of Receivable (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Receivables [Abstract]
Accounts receivable	$ 137,953	$ 199,720
Unbilled receivables	208,823	180,219
Long-term unbilled receivables	108,456	121,736
Total receivables	$ 455,232	$ 501,675

Amount, after allowance for credit loss, of right to consideration from customer for product sold and service rendered in normal course of business, classified as current.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
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-SubTopic 10
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Reference 2: http://www.xbrl.org/2003/role/disclosureRef
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-Name Accounting Standards Codification
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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant