EMPLOYEE BENEFITS - Benefit Plan (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Employee Benefits and Share-based Compensation [Abstract]
Percentage of participant's contribution matched by Company	100.00%
Percentage of participant's salary matched by Company	6.00%
Company contributions	$ 1.4	$ 1.3	$ 1.0

Percentage of employees' gross pay for which the employer contributes a matching contribution to a defined contribution plan.

No definition available.

Name:	us-gaap_DefinedContributionPlanEmployerMatchingContributionPercent
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration