DISPOSITIONS AND SPECIAL (GAINS) CHARGES - Special Charges (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
NATG and Corporate
Restructuring Reserve [Roll Forward]
Balance beginning of period	$ 20.2
Charged to expense	2.5
Paid or otherwise settled	(15.6)
Balance end of period	7.1	$ 20.2
ETG, NATG, and Corporate
Restructuring Reserve [Roll Forward]
Balance beginning of period	20.2	20.5
Charged to expense		6.8
Paid or otherwise settled		(7.1)
Balance end of period		20.2
Lease liabilities and other costs | Corporate
Restructuring Reserve [Roll Forward]
Balance beginning of period	1.2	1.2
Charged to expense	0.0	0.0
Paid or otherwise settled	(0.3)	0.0
Balance end of period	0.9	1.2
Lease liabilities and other costs | NATG
Restructuring Reserve [Roll Forward]
Balance beginning of period	19.0	19.3
Charged to expense	2.5	6.5
Paid or otherwise settled	(15.3)	(6.8)
Balance end of period	6.2	19.0
Workforce reduction and other personnel costs | ETG
Restructuring Reserve [Roll Forward]
Balance beginning of period	$ 0.0	0.0
Charged to expense		0.3
Paid or otherwise settled		(0.3)
Balance end of period		$ 0.0