Pension and Other Postretirement Benefits (Tables)

9 Months Ended

Sep. 30, 2016

Compensation and Retirement Disclosure [Abstract]

Net periodic pension and OPEB cost

Pension and Other Postretirement Benefits("OPEB")

	For the Three Months Ended
	September 30, 2016								September 30, 2015
	Pension			OPEB		Consolidated			Pension			OPEB			Consolidated
	(In millions)
Net periodic pension and OPEB cost:
Service cost - benefits earned during the year	$	1.9		$	0.4	$	2.3		$	2.1		$	0.7		$	2.8
Interest cost on projected benefit obligation	31.0			1.5		32.5			33.9			1.6			35.5
Expected return on plan assets	(38.0		)	—		(38.0		)	(44.0		)	—			(44.0		)
Amortization of prior service cost (benefit)	0.2			0.1		0.3			0.2			(0.4		)	(0.2		)
Amortization of net actuarial loss	7.4			—		7.4			12.1			—			12.1
Less: expected participant contributions	(0.1		)	—		(0.1		)	(0.2		)	—			(0.2		)
Net periodic pension and OPEB cost	$	2.4		$	2.0	$	4.4		$	4.1		$	1.9		$	6.0

	For the Nine Months Ended
	September 30, 2016								September 30, 2015
	Pension			OPEB		Consolidated			Pension			OPEB			Consolidated
	(In millions)
Net periodic pension and OPEB cost:
Service cost - benefits earned during the year	$	5.7		$	1.6	$	7.3		$	7.3		$	1.6		$	8.9
Interest cost on projected benefit obligation	95.5			4.4		99.9			103.2			4.6			107.8
Expected return on plan assets	(118.0		)	—		(118.0		)	(132.7		)	—			(132.7		)
Amortization of prior service cost (benefit)	0.6			—		0.6			0.6			(0.6		)	—
Amortization of net actuarial loss	23.0			—		23.0			35.2			—			35.2
Curtailment gain	—			—		—			(1.0		)	—			(1.0		)
Less: expected participant contributions	(0.4		)	—		(0.4		)	(0.6		)	—			(0.6		)
Net periodic pension and OPEB cost	$	6.4		$	6.0	$	12.4		$	12.0		$	5.6		$	17.6