PENSION BENEFITS AND POSTRETIREMENT BENEFITS OTHER THAN PENSION - Narrative (Details) - USD ($) $ in Millions	9 Months Ended
Sep. 30, 2019	Sep. 30, 2018
Pension Plans
Defined Benefit Plan Disclosure [Line Items]
Contributions to defined benefit plans	$ 112.5	$ 183.2
PBOP
Defined Benefit Plan Disclosure [Line Items]
Contributions to defined benefit plans	$ 7.9	$ 5.7

Amount of contribution received by defined benefit plan from employer which increases plan assets.

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Name:	us-gaap_DefinedBenefitPlanContributionsByEmployer
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration