EMPLOYEE BENEFITS (Tables)

3 Months Ended

Mar. 31, 2018

Retirement Benefits [Abstract]

Schedule of Net Benefit Costs

The following tables show the components of net periodic pension and OPEB costs for our benefit plans.

	Pension Costs
	Three Months Ended March 31
(in millions)	2018			2017
Service cost	$	12.0		$	11.7
Interest cost	28.3			31.2
Expected return on plan assets	(49.6		)	(49.6		)
Loss on plan settlement	0.4			—
Amortization of prior service cost	0.7			0.7
Amortization of net actuarial loss	23.1			21.9
Net periodic benefit cost	$	14.9		$	15.9

	OPEB Costs
	Three Months Ended March 31
(in millions)	2018			2017
Service cost	$	6.2		$	6.3
Interest cost	7.5			8.5
Expected return on plan assets	(14.9		)	(13.7		)
Amortization of prior service credit	(3.8		)	(2.8		)
Amortization of net actuarial loss	0.3			1.5
Net periodic benefit credit	$	(4.7	)	$	(0.2	)

Schedule of retroactively restated Income Statement

The impacts to our income statements from adoption of this standard are reflected in the table below.

	Year Ended December 31, 2017						Year Ended December 31, 2016							Year Ended December 31, 2015
(in millions)	Form 10-K Income Statement		Impact of ASU 2017-07		Income Statement After Adoption		Form 10-K Income Statement		Impact of ASU 2017-07			Income Statement After Adoption		Form 10-K Income Statement		Impact of ASU 2017-07		Income Statement After Adoption
Operating expenses
Other operation and maintenance	$	2,047.0	$	9.1	$	2,056.1	$	2,185.5	$	(14.2	)	$	2,171.3	$	1,709.3	$	1.4	$	1,710.7
Other expense
Other income, net	64.6		9.1		73.7		80.8		(14.2		)	66.6		58.9		1.4		60.3