Postretirement and Other Benefits (Tables)

3 Months Ended

Mar. 31, 2020

Retirement Benefits [Abstract]

Net Pension Benefit Costs

The components of net pension and OPEB benefit costs for U.S. employees and net pension benefit costs for French employees during the three months ended March 31, 2020 and 2019 were as follows ($ in millions):

	Three Months Ended March 31,
	U.S. Pension Benefits						French Pension Benefits				U.S. OPEB Benefits
	2020			2019			2020		2019		2020		2019
Service cost	$	—		$	—		$	0.3	$	0.2	$	—	$	—
Interest cost	0.9			1.2			—		0.1		—		—
Expected return on plan assets	(1.2		)	(1.5		)	—		—		—		—
Amortizations and other	0.8			0.5			0.3		0.2		—		—
Net periodic benefit cost	$	0.5		$	0.2		$	0.6	$	0.5	$	—	$	—