Benefit Plans (Tables)

9 Months Ended

Sep. 30, 2021

Entity Information [Line Items]

Schedule of Net Periodic Benefit Cost / (Income)

The net periodic benefit cost of the pension benefit plans for the three and nine months ended September 30, 2021 and 2020 was:

	Three months ended				Nine months ended
	September 30,				September 30,
$ in millions	2021		2020		2021		2020
Service cost	$	1.2	$	0.9	$	3.4	$	2.8
Interest cost	2.1		2.9		6.1		8.8
Expected return on plan assets	(3.8)		(4.6)		(11.2)		(14.0)
Amortization of unrecognized:
Prior service cost	0.2		0.3		0.6		0.8
Actuarial loss	2.2		1.5		6.8		4.6
Net periodic benefit cost	$	1.9	$	1.0	$	5.7	$	3.0

Subsidiaries [Member]

Entity Information [Line Items]

Schedule of Net Periodic Benefit Cost / (Income)

The net periodic benefit cost of the pension benefit plans for the three and nine months ended September 30, 2021 and 2020 was:

	Three months ended				Nine months ended
	September 30,				September 30,
$ in millions	2021		2020		2021		2020
Service cost	$	1.2	$	0.9	$	3.4	$	2.8
Interest cost	2.1		2.9		6.1		8.8
Expected return on plan assets	(3.8)		(4.6)		(11.2)		(14.0)
Amortization of unrecognized:
Prior service cost	0.2		0.3		0.8		1.0
Actuarial loss	2.9		2.2		8.5		6.5
Net periodic benefit cost	$	2.6	$	1.7	$	7.6	$	5.1