Employee Benefit Plans and Other Postretirement Benefits (Tables)

6 Months Ended

Jun. 30, 2017

Compensation And Retirement Disclosure [Abstract]

Components of Net Periodic Benefit Costs

The components of net periodic benefit cost for our pension plans were as follows (dollars in millions):

	Pension Plans
	Three Months Ended June 30,						Six Months Ended June 30,
	2017			2016			2017			2016
Service cost	$	6.1		$	6.1		$	12.2		$	12.2
Interest cost		10.4			10.2			20.8			20.4
Expected return on plan assets		(13.5	)		(12.4	)		(27.0	)		(24.8	)
Net amortization of unrecognized amounts
Prior service cost		1.5			1.4			3.0			2.8
Actuarial loss		1.9			1.4			3.7			2.8
Net periodic benefit cost	$	6.4		$	6.7		$	12.7		$	13.4

The components of net periodic benefit cost for our postretirement plans were as follows (dollars in millions):

	Postretirement Plans
	Three Months Ended June 30,						Six Months Ended June 30,
	2017			2016			2017			2016
Service cost	$	0.1		$	0.2		$	0.2		$	0.4
Interest cost		0.2			0.2			0.3			0.4
Net amortization of unrecognized amounts
Prior service cost		(0.1	)		—			(0.1	)		—
Actuarial loss		—			(0.2	)		—			(0.4	)
Net periodic benefit cost	$	0.2		$	0.2		$	0.4		$	0.4