LEASE COMMITMENTS - Future Minimum Lease Payments and Rent Expense (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Future minimum payments under operating leases
2018	$ 1,072
2019	1,072
2020	1,072
2021	1,072
2022	1,072
Total minimum lease payments	5,360
Operating lease expense
Rental expense for operating leases	$ 1,600	$ 1,500	$ 1,000