Postretirement and Other Benefits (Tables)

9 Months Ended

Sep. 30, 2019

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 or nine months ended September 30, 2019 and 2018 were as follows ($ in millions):

	Three Months Ended September 30,
	U.S. Pension Benefits						French Pension Benefits					U.S. OPEB Benefits
	2019			2018			2019			2018		2019		2018
Service cost	$	—		$	—		$	0.3		$	0.2	$	—	$	—
Interest cost	1.2			1.0			0.1			0.1		—		—
Expected return on plan assets	(1.5		)	(1.5		)	(0.1		)	—		—		—
Amortizations and other	0.5			0.7			0.2			0.2		—		0.1
Net periodic benefit cost	$	0.2		$	0.2		$	0.5		$	0.5	$	—	$	0.1

	Nine Months Ended September 30,
	U.S. Pension Benefits						French Pension Benefits						U.S. OPEB Benefits
	2019			2018			2019			2018			2019		2018
Service cost	$	—		$	—		$	0.8		$	0.8		$	—	$	—
Interest cost	3.5			3.2			0.3			0.3			—		—
Expected return on plan assets	(4.4		)	(4.4		)	(0.1		)	(0.1		)	—		—
Amortizations and other	1.5			2.4			0.6			0.6			—		0.2
Net periodic benefit cost	$	0.6		$	1.2		$	1.6		$	1.6		$	—	$	0.2