Employee Benefits (Tables)

9 Months Ended

Sep. 30, 2016

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 OPEB costs for our benefit plans:

	Pension Costs
	Three Months Ended September 30						Nine Months Ended September 30
(in millions)	2016			2015			2016			2015
Service cost	$	2.7		$	3.7		$	7.9		$	11.0
Interest cost	12.4			13.3			37.3			39.7
Expected return on plan assets	(19.5		)	(20.9		)	(58.3		)	(62.7		)
Amortization of prior service cost	0.4			0.5			1.2			1.5
Amortization of net actuarial loss	8.1			8.8			24.3			26.7
Net periodic benefit cost	$	4.1		$	5.4		$	12.4		$	16.2

	OPEB Costs
	Three Months Ended September 30						Nine Months Ended September 30
(in millions)	2016			2015			2016			2015
Service cost	$	1.9		$	2.2		$	5.5		$	6.7
Interest cost	3.3			3.4			9.9			10.1
Expected return on plan assets	(3.5		)	(4.0		)	(10.5		)	(12.0		)
Amortization of prior service credit	(0.3		)	(0.2		)	(0.8		)	(0.8		)
Amortization of net actuarial loss	0.2			0.1			0.7			0.7
Net periodic benefit cost	$	1.6		$	1.5		$	4.8		$	4.7