REVENUE RECOGNITION - Additional Information (Details) - USD ($) $ in Thousands	3 Months Ended										12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017		Sep. 30, 2017	Jun. 30, 2017	[1]	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Disaggregation Of Revenue [Line Items]
Deferred revenue											$ 130,639	$ 8,402	$ 3,360
Deferred revenue offset by reduction of retained earnings					$ 17,100							17,100
Revenue	$ 70,143	$ 77,550	$ 56,149	$ 43,572	$ 115,867	[1],[2]	$ 61,683	$ 102,513		$ 55,566	$ 247,414	$ 335,629	$ 198,886
Contract expiration year											2022
Backlog associated with committed purchase orders from customers	13,100										$ 13,100
Revenue from Contracts with Customers - ASU No. 2014-09 [Member]
Disaggregation Of Revenue [Line Items]
Deferred revenue											21,300
Deferred revenue offset by reduction of retained earnings	17,100										17,100
Deferred revenue offset by reduction of retained earnings, tax amount											3,900
Unbilled receivables	$ 300										300
Revenue											$ 78,900
Percentage of revenue recorded from sales of materials											95.00%	97.00%	98.00%
Revenue from Contracts with Customers - ASU No. 2014-09 [Member] | Adesis, Inc. [Member]
Disaggregation Of Revenue [Line Items]
Percentage of revenue recorded from provision of services											5.00%	3.00%	2.00%

[1] Prior to the adoption of ASC 606 on January 1, 2018, the Company recorded as revenue the receipt of the semi-annual license fee payment of $45.0 million from SDC in the second and fourth quarters.

[2] The enactment of the Tax Cuts and Jobs Act in December 2017 resulted in a one-time charge of $11.5 million in the fourth quarter.