COMMITMENTS AND CONTINGENCIES - Rental Expense and Surety Bonds (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
COMMITMENTS AND CONTINGENCIES
Rental expense	$ 0.4	$ 0.5	$ 0.5
Outstanding surety bonds	$ 4.8	$ 4.8
Percentage of annual fees on surety bonds	1.50%
Percentage of upfront deposit on surety bonds	10.00%
Surety bonds upfront deposit amount	$ 0.5