Benefit Plans (Tables)

6 Months Ended

Jun. 30, 2019

Defined Benefit Plans and Other Postretirement Benefit Plans Disclosures [Abstract]

Schedule of Components of Net Periodic Benefit Cost

The components of net periodic benefit cost for the three months ended June 30 were as follows:

	Pension benefits						Other retirement benefits						Total
($ in millions)	2019			2018			2019			2018			2019			2018
Service cost	$	0.3		$	2.7		$	—		$	—		$	0.3		$	2.7
Interest cost	2.5			2.4			—			—			2.5			2.4
Expected return on assets	(2.9		)	(3.9		)	—			—			(2.9		)	(3.9		)
Amortization of prior service credit	—			(0.5		)	(0.1		)	(0.1		)	(0.1		)	(0.6		)
Recognized actuarial losses (gains)	0.6			1.0			(0.6		)	(0.6		)	—			0.4
Net periodic benefit cost	$	0.5		$	1.7		$	(0.7	)	$	(0.7	)	$	(0.2	)	$	1.0

	Pension benefits				Other retirement benefits						Total
($ in millions)	2019		2018		2019			2018			2019			2018
U.S. plans	$	—	$	1.2	$	(0.7	)	$	(0.7	)	$	(0.7	)	$	0.5
International plans	0.5		0.5		—			—			0.5			0.5
Net periodic benefit cost	$	0.5	$	1.7	$	(0.7	)	$	(0.7	)	$	(0.2	)	$	1.0

The components of net periodic benefit cost for the six months ended June 30 were as follows:

	Pension benefits						Other retirement benefits						Total
($ in millions)	2019			2018			2019			2018			2019			2018
Service cost	$	0.7		$	5.5		$	—		$	—		$	0.7		$	5.5
Interest cost	4.9			4.7			0.1			0.1			5.0			4.8
Expected return on assets	(5.8		)	(7.8		)	—			—			(5.8		)	(7.8		)
Amortization of prior service credit	—			(0.8		)	(0.3		)	(0.3		)	(0.3		)	(1.1		)
Recognized actuarial losses (gains)	1.1			1.9			(1.1		)	(1.1		)	—			0.8
Net periodic benefit cost	$	0.9		$	3.5		$	(1.3	)	$	(1.3	)	$	(0.4	)	$	2.2

	Pension benefits					Other retirement benefits						Total
($ in millions)	2019			2018		2019			2018			2019			2018
U.S. plans	$	(0.1	)	$	2.5	$	(1.3	)	$	(1.3	)	$	(1.4	)	$	1.2
International plans	1.0			1.0		—			—			1.0			1.0
Net periodic benefit cost	$	0.9		$	3.5	$	(1.3	)	$	(1.3	)	$	(0.4	)	$	2.2