DEFINED CONTRIBUTION PLAN (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
DEFINED CONTRIBUTION PLAN
Company's expense under matching requirements	$ 5.7	$ 3.7	$ 2.4
Employer contributions		$ 0.4	$ 0.2

Amount of contribution received by defined benefit plan from employer which increases plan assets.

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Name:	us-gaap_DefinedBenefitPlanContributionsByEmployer
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration