Retirement Benefits (Tables)

6 Months Ended

Jun. 30, 2018

Retirement Benefits [Abstract]

Schedule of Components of Retirement Benefit Expense (Benefit)

Components of retirement benefits expense (income) are:

	Pension Benefits						Postretirement Medical and Life Insurance Benefits
	Three months ended June 30,
	2018			2017			2018			2017
	(In millions)
Interest cost on benefit obligation	$	12.5		$	14.4		$	0.3		$	0.3
Assumed return on plan assets	(15.1		)	(12.4		)	—			—
Amortization of prior service costs	0.1			0.1			—			—
Recognized net actuarial losses (gains)	17.6			16.9			(1.0		)	(1.0		)
Retirement benefits expense (income)	$	15.1		$	19.0		$	(0.7	)	$	(0.7	)

	Pension Benefits						Postretirement Medical and Life Insurance Benefits
	Six months ended June 30,
	2018			2017			2018			2017
	(In millions)
Interest cost on benefit obligation	$	24.9		$	28.8		$	0.6		$	0.7
Assumed return on plan assets	(30.1		)	(24.8		)	—			—
Amortization of prior service costs (credits)	0.1			0.1			(0.1		)	(0.1		)
Recognized net actuarial losses (gains)	35.3			33.9			(1.9		)	(2.0		)
Retirement benefits expense (income)	$	30.2		$	38.0		$	(1.4	)	$	(1.4	)