Benefit Plans (Tables)

3 Months Ended

Mar. 31, 2021

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 March 31 were as follows:

	Pension benefits				Other retirement benefits				Total
($ in millions)	2021		2020		2021		2020		2021		2020
Service cost	$	0.4	$	0.3	$	—	$	—	$	0.4	$	0.3
Interest cost	1.4		1.9		0.1		0.1		1.5		2.0
Expected return on assets	(3.1)		(3.0)		—		—		(3.1)		(3.0)
Amortization of prior service credit	—		—		(0.1)		(0.2)		(0.1)		(0.2)
Recognized actuarial losses (gains)	0.5		0.5		(0.4)		(0.4)		0.1		0.1
Settlements	0.6		1.4		—		—		0.6		1.4
Net periodic benefit cost	$	(0.2)	$	1.1	$	(0.4)	$	(0.5)	$	(0.6)	$	0.6

	Pension benefits				Other retirement benefits				Total
($ in millions)	2021		2020		2021		2020		2021		2020
U.S. plans	$	(0.6)	$	0.8	$	(0.4)	$	(0.5)	$	(1.0)	$	0.3
International plans	0.4		0.3		—		—		0.4		0.3
Net periodic benefit cost	$	(0.2)	$	1.1	$	(0.4)	$	(0.5)	$	(0.6)	$	0.6