DEBT - Schedule of Line of Credit Facilities (Details) - Secured Debt - Credit Facility	6 Months Ended
	Jun. 30, 2019 USD ($)	Dec. 31, 2018 USD ($)
Line of Credit Facility [Line Items]
Aggregate borrowing capacity under Credit Agreement	$ 385,000,000	$ 385,000,000
Available under credit agreement	$ 168,400,000	175,400,000
Borrowing capacity limit multiple of EBITDA	4.5
EBITDA multiple cap	$ 34,000,000
Revolving Credit Facility
Line of Credit Facility [Line Items]
Long-term line of credit	216,000,000	209,000,000
Letters of Credit
Line of Credit Facility [Line Items]
Long-term line of credit	$ 600,000	$ 600,000