Employee Benefits (Tables)

9 Months Ended

Sep. 30, 2015

Compensation and Retirement Disclosure [Abstract]

Schedule of the components of net periodic benefit cost

The following tables show the components of net periodic pension and other postretirement employee benefits (OPEB) costs for our benefit plans. Our pension and OPEB costs for the three and nine months ended September 30, 2015, include costs attributable to the Integrys pension and OPEB plans that were incurred subsequent to the acquisition of Integrys on June 29, 2015. The terms and conditions of the legacy company plans have not changed since the acquisition.

	Pension Costs
	Three Months Ended September 30						Nine Months Ended September 30
(in millions)	2015			2014			2015			2014
Service cost	$	11.3		$	2.6		$	19.1		$	7.6
Interest cost	31.9			17.0			62.2			51.1
Expected return on plan assets	(52.1		)	(24.7		)	(103.5		)	(74.0		)
Amortization of:
Prior service cost	0.7			0.6			1.7			1.6
Net actuarial loss	22.7			9.1			45.7			27.5
Net periodic benefit cost	$	14.5		$	4.6		$	25.2		$	13.8

	OPEB Costs
	Three Months Ended September 30						Nine Months Ended September 30
(in millions)	2015			2014			2015			2014
Service cost	$	8.0		$	2.1		$	12.7		$	6.4
Interest cost	9.3			4.4			17.4			13.3
Expected return on plan assets	(13.9		)	(5.9		)	(25.7		)	(17.8		)
Amortization of:
Prior service credit	(2.9		)	(0.4		)	(3.5		)	(1.3		)
Net actuarial loss	1.5			0.3			2.5			0.9
Net periodic benefit cost	$	2.0		$	0.5		$	3.4		$	1.5