COMMITMENTS, CONTINGENCIES AND OTHER MATTERS - Narrative (Details) $ in Millions	12 Months Ended
	Dec. 31, 2017 USD ($) officer state	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)
Loss Contingencies [Line Items]
Number of principal shareholders and senior executive officers | officer	3
Annual rent expense	$ 13.5	$ 17.7	$ 26.4
Related party rent expense	0.9	0.9	1.0
Rent expense net of sublease income	$ 0.4	0.4	0.1
Number of states seeking recovery of unclaimed property | state	21
NATG
Loss Contingencies [Line Items]
Annual rent expense	$ 0.8	$ 5.2	$ 14.2