PENSION AND POST-RETIREMENT PLANS - STATUS (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Pension Benefits
Change in Benefit Obligation:
Benefit obligation at beginning of year	$ 232.1	$ 225.4
Service cost	4.4	4.0	$ 3.9
Interest cost	8.6	9.7	9.7
Plan settlements		(0.3)
Actuarial (gain) loss	(14.1)	13.9
Benefits paid, net of subsidies received	(12.0)	(18.9)
Expenses paid	(1.6)	(1.7)
Benefit obligation at end of year	217.4	232.1	225.4
Change in Plan Assets:
Balance at the beginning of the period	186.7	178.8
Actual return on plan assets	(10.9)	25.8
Plan settlements		(0.3)
Employer contribution	0.0	3.0	7.5
Benefits paid, net of subsidies received	(12.0)	(18.9)
Expenses paid	(1.6)	(1.7)
Balance at the end of the period	162.2	186.7	178.8
Funded Status and Recognized Liability	(55.2)	(45.4)
Post-retirement Benefits
Change in Benefit Obligation:
Benefit obligation at beginning of year	27.7	25.2
Service cost	0.6	0.5	1.5
Interest cost	1.0	1.1	2.7
Plan participants' contributions	0.9	1.1
Actuarial (gain) loss	(6.2)	1.9
Benefits paid, net of subsidies received	(1.8)	(2.1)
Benefit obligation at end of year	22.2	27.7	$ 25.2
Change in Plan Assets:
Plan participants' contributions	0.9	1.1
Employer contribution	0.9	1.0
Benefits paid, net of subsidies received	(1.8)	(2.1)
Funded Status and Recognized Liability	(22.2)	(27.7)
Qualified Plan | Pension Benefits
Change in Benefit Obligation:
Benefit obligation at beginning of year	229.9
Benefit obligation at end of year	215.9	229.9
Change in Plan Assets:
Balance at the beginning of the period	184.7
Balance at the end of the period	$ 159.9	$ 184.7