PENSION AND OTHER POSTRETIREMENT BENEFITS (Effect of Fair Value Measurements Using Significant Unobservable Inputs (Level 3) on Changes in Other Benefit Plan Assets) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value of plan assets — beginning of year	$ 202.4	$ 193.4
Actual return on plan assets:
Relating to assets still held at the reporting date	16.1	12.3
Acquired through business combinations	57.9	8.0
Sales	65.6	14.6
Fair value of plan assets — end of year	215.6	202.4
Hedge Funds [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value of plan assets — beginning of year	40.6	40.7
Actual return on plan assets:
Relating to assets still held at the reporting date	2.5	(0.1)
Acquired through business combinations	39.0	0.0
Sales	45.1	0.0
Fair value of plan assets — end of year	37.4	40.6
Private Equity Funds [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value of plan assets — beginning of year	36.1	33.1
Actual return on plan assets:
Relating to assets still held at the reporting date	0.3	(2.7)
Acquired through business combinations	4.5	8.0
Sales	5.6	6.0
Fair value of plan assets — end of year	39.8	36.1
Real Estate [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value of plan assets — beginning of year	61.9	57.5
Actual return on plan assets:
Relating to assets still held at the reporting date	4.2	5.1
Acquired through business combinations	14.4	0.0
Sales	14.9	0.6
Fair value of plan assets — end of year	65.5	61.9
Other Benefits [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value of plan assets — beginning of year	253.0	250.6
Actual return on plan assets:
Fair value of plan assets — end of year	262.5	253.0
Other Benefits [Member] | Hedge Funds [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value of plan assets — beginning of year	11.2
Actual return on plan assets:
Fair value of plan assets — end of year	11.4	11.2
Other Benefits [Member] | Private Equity Funds [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value of plan assets — beginning of year	4.3
Actual return on plan assets:
Fair value of plan assets — end of year	3.9	4.3
Other Benefits [Member] | Structured Credit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value of plan assets — beginning of year	6.9
Actual return on plan assets:
Fair value of plan assets — end of year	7.9	6.9
Other Benefits [Member] | Real Estate [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value of plan assets — beginning of year	11.1
Actual return on plan assets:
Fair value of plan assets — end of year	12.0	11.1
Significant Unobservable Inputs (Level 3) [Member] | Other Benefits [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value of plan assets — beginning of year	33.5	32.5
Actual return on plan assets:
Relating to assets still held at the reporting date	7.1	1.9
Acquired through business combinations	24.0	0.0
Sales	25.5	1.0
Fair value of plan assets — end of year	35.2	33.5
Significant Unobservable Inputs (Level 3) [Member] | Other Benefits [Member] | Hedge Funds [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value of plan assets — beginning of year	11.2	11.2
Actual return on plan assets:
Relating to assets still held at the reporting date	0.8	0.0
Acquired through business combinations	17.1	0.0
Sales	17.7	0.0
Fair value of plan assets — end of year	11.4	11.2
Significant Unobservable Inputs (Level 3) [Member] | Other Benefits [Member] | Private Equity Funds [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value of plan assets — beginning of year	4.3	5.5
Actual return on plan assets:
Relating to assets still held at the reporting date	0.9	(0.3)
Acquired through business combinations	1.8	0.0
Sales	2.7	1.0
Fair value of plan assets — end of year	3.9	4.3
Significant Unobservable Inputs (Level 3) [Member] | Other Benefits [Member] | Structured Credit [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value of plan assets — beginning of year	6.9	5.8
Actual return on plan assets:
Relating to assets still held at the reporting date	2.0	1.1
Acquired through business combinations	2.1	0.0
Sales	2.1	0.0
Fair value of plan assets — end of year	7.9	6.9
Significant Unobservable Inputs (Level 3) [Member] | Other Benefits [Member] | Real Estate [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Fair value of plan assets — beginning of year	11.1	10.0
Actual return on plan assets:
Relating to assets still held at the reporting date	3.4	1.1
Acquired through business combinations	3.0	0.0
Sales	3.0	0.0
Fair value of plan assets — end of year	$ 12.0	$ 11.1