Retirement Benefits (Tables)

9 Months Ended

Sep. 30, 2017

Retirement Benefits [Abstract]

Schedule of Components of Retirement Benefit Expense (Benefit)

Components of retirement benefit expense (benefit) are:

	Pension Benefits						Postretirement Medical and Life Insurance Benefits
	Three months ended September 30,
	2017			2016			2017			2016
	(In millions)
Service cost	$	3.7		$	3.6		$	—		$	—
Interest cost on benefit obligation	14.4			16.0			0.4			0.5
Assumed return on plan assets	(16.1		)	(17.5		)	—			—
Amortization of prior service credits	—			—			—			(0.3		)
Recognized net actuarial losses (gains)	17.0			15.9			(1.1		)	(0.9		)
Retirement benefit expense (benefit)	$	19.0		$	18.0		$	(0.7	)	$	(0.7	)

	Pension Benefits						Postretirement Medical and Life Insurance Benefits
	Nine months ended September 30,
	2017			2016			2017			2016
	(In millions)
Service cost	$	11.2		$	10.5		$	—		$	—
Interest cost on benefit obligation	43.2			48.1			1.1			1.4
Assumed return on plan assets	(48.4		)	(52.6		)	—			—
Amortization of prior service credits	0.1			0.1			(0.1		)	(0.9		)
Recognized net actuarial losses (gains)	50.9			47.8			(3.1		)	(2.7		)
Retirement benefit expense (benefit)	$	57.0		$	53.9		$	(2.1	)	$	(2.2	)