Retirement Benefits (Tables)

9 Months Ended

Sep. 30, 2021

Retirement Benefits [Abstract]

Schedule of Components of Retirement Benefit Expense (Benefit)

The following table presents the components of retirement benefits expense (income): 

	Pension Benefits				Postretirement Medical and Life Insurance Benefits
	Three months ended September 30,
	2021		2020		2021		2020
	(In millions)
Interest cost on benefit obligation	$	8.4	$	10.7	$	0.1	$	0.2
Expected return on assets	(15.3)		(15.2)		—		—
Amortization of prior service costs	—		—		—		—
Amortization of net losses (gains)	16.0		14.3		(0.7)		(0.9)
Retirement benefits expense (income)	$	9.1	$	9.8	$	(0.6)	$	(0.7)

	Pension Benefits				Postretirement Medical and Life Insurance Benefits
	Nine months ended September 30,
	2021		2020		2021		2020
	(In millions)
Interest cost on benefit obligation	$	25.1	$	31.9	$	0.4	$	0.6
Expected return on assets	(46.0)		(45.4)		—		—
Amortization of prior service costs	0.1		0.1		—		—
Amortization of net losses (gains)	47.9		43.0		(2.1)		(2.8)
Retirement benefits expense (income)	$	27.1	$	29.6	$	(1.7)	$	(2.2)