PROPERTY, PLANT AND EQUIPMENT - Schedule of Property, Plant, and Equipment (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	$ 58.2	$ 55.3
Less accumulated depreciation and amortization	40.4	40.4
Property, plant and equipment, net	17.8	14.9
Depreciation	3.9	3.5	$ 3.6
Land improvements
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	0.8	0.8
Furniture and fixtures, office, computer and other equipment and software
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	44.3	42.8
Leasehold improvements
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	13.1	11.7
NATG and ETG
Property, Plant and Equipment [Line Items]
Depreciation, discontinued operations	$ 0.0	$ 0.3	$ 0.7