Pension and Other Postretirement Benefits (Tables)

6 Months Ended

Jun. 30, 2016

Compensation and Retirement Disclosure [Abstract]

Net periodic pension and OPEB cost

Pension and Other Postretirement Benefits("OPEB")

	For the Three Months Ended
	June 30, 2016									June 30, 2015
	Pension			OPEB			Consolidated			Pension			OPEB			Consolidated
	(In millions)
Net periodic pension and OPEB cost:
Service cost - benefits earned during the year	$	2.0		$	0.6		$	2.6		$	2.6		$	0.4		$	3.0
Interest cost on projected benefit obligation	32.6			1.6			34.2			34.9			1.5			36.4
Expected return on plan assets	(40.5		)	—			(40.5		)	(44.6		)	—			(44.6		)
Amortization of prior service cost (benefit)	0.2			(0.1		)	0.1			0.2			(0.1		)	0.1
Amortization of net actuarial loss	7.9			—			7.9			11.9			—			11.9
Less: expected participant contributions	(0.2		)	—			(0.2		)	(0.2		)	—			(0.2		)
Net periodic pension and OPEB cost	$	2.0		$	2.1		$	4.1		$	4.8		$	1.8		$	6.6

	For the Six Months Ended
	June 30, 2016									June 30, 2015
	Pension			OPEB			Consolidated			Pension			OPEB			Consolidated
	(In millions)
Net periodic pension and OPEB cost:
Service cost - benefits earned during the year	$	3.8		$	1.2		$	5.0		$	5.2		$	0.9		$	6.1
Interest cost on projected benefit obligation	64.5			2.9			67.4			69.3			3.0			72.3
Expected return on plan assets	(80.0		)	—			(80.0		)	(88.7		)	—			(88.7		)
Amortization of prior service cost (benefit)	0.4			(0.1		)	0.3			0.4			(0.2		)	0.2
Amortization of net actuarial loss	15.6			—			15.6			23.1			—			23.1
Curtailment gain	—			—			—			(1.0		)	—			(1.0		)
Less: expected participant contributions	(0.3		)	—			(0.3		)	(0.4		)	—			(0.4		)
Net periodic pension and OPEB cost	$	4.0		$	4.0		$	8.0		$	7.9		$	3.7		$	11.6