RECEIVABLES, CONTRACT ASSETS, AND DEFERRED REVENUE - Summary of Receivable (Details) - USD ($) $ in Thousands		Dec. 31, 2018	Dec. 31, 2017
Receivables [Abstract]
Accounts receivable	[1]	$ 180,872	$ 222,735
Unbilled receivables	[1]	172,656	160,084
Long-term unbilled receivables	[1]	151,237	160,708
Total receivables		$ 504,765	$ 543,527

[1] On January 1, 2018, the Company adopted the ASC 606 revenue recognition standard and adjusted prior periods to conform. See "Note 2. Significant Accounting Policies" for additional information.