REVENUE - Activity in Contract Assets and Liabilities (Details) - USD ($) $ in Thousands	6 Months Ended
Jun. 30, 2018	Dec. 31, 2017
Disaggregation of Revenue [Line Items]
Unbilled revenue, billed upon passage of time	$ 22,000	$ 14,300
Deferred revenue, current	6,120	3,201
Movement in Contract Assets [Roll Forward]
Balance as of December 31, 2017	274,699
Additions	12,295
Transfers to Receivables	(32,488)
June 30, 2018	254,506
Movement in Deferred Revenue [Roll Forward]
Balance as of December 31, 2017	3,201
Additions	5,949
Transfers to Revenues	(3,030)
June 30, 2018	6,120
Unbilled Revenues, Current
Disaggregation of Revenue [Line Items]
Contract assets, current	35,600	49,600
Unbilled Revenues, Less Current Portion
Disaggregation of Revenue [Line Items]
Contract assets, noncurrent	$ 218,900	$ 225,200

Amount, after allowance for credit loss, of right to consideration in exchange for good or service transferred to customer when right is conditioned on something other than passage of time.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
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Unbilled amounts due for services rendered or to be rendered, actions taken or to be taken, or a promise to refrain from taking certain actions in accordance with the terms of a legally binding agreement between the entity and, at a minimum, one other party. An example would be amounts associated with contracts or programs where the recognized revenue for performance thereunder exceeds the amounts billed under the terms thereof as of the date of the balance sheet.

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Contract with Customer, Asset, Additions

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Movement in Contract Assets [Roll Forward]

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