REVENUE RECOGNITION - Schedule of Assets and Liabilities Associated with Contracts from Customers (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Disaggregation Of Revenue [Line Items]
Accounts receivable	$ 65,774	$ 43,129
Short-term deferred revenue	91,188	80,782
Long-term deferred revenue	50,495	$ 41,785
Other Current Assets [Member]
Disaggregation Of Revenue [Line Items]
Short-term unbilled receivables	467
Other Assets [Member]
Disaggregation Of Revenue [Line Items]
Long-term unbilled receivables	$ 6,899