Retirement Benefits (Tables)

6 Months Ended

Mar. 31, 2023

Retirement Benefits [Abstract]

Schedule of Net Benefit Costs

The components of net periodic pension and postretirement benefit cost were (in millions):

	Pension Benefits
	Three Months Ended March 31,				Six Months Ended March 31,
	2023		2022		2023		2022
Service cost	$	10.6	$	20.3	$	21.2	$	40.7
Interest cost	39.5		32.4		78.7		64.8
Expected return on plan assets	(51.7)		(59.3)		(103.0)		(118.7)
Amortization of prior service cost	—		0.8		—		0.8
Amortization of net actuarial (gain) loss	(1.0)		22.3		(2.0)		44.6
Settlement charge	117.9		24.9		117.9		24.9
Net periodic pension benefit cost	$	115.3	$	41.4	$	112.8	$	57.1

	Other Postretirement Benefits
	Three Months Ended March 31,				Six Months Ended March 31,
	2023		2022		2023		2022
Service cost	$	0.1	$	0.2	$	0.2	$	0.4
Interest cost	0.5		0.3		1.1		0.6
Amortization of prior service credit	—		(0.2)		—		(0.4)
Amortization of net actuarial loss	0.2		0.1		0.3		0.3
Net periodic postretirement benefit cost	$	0.8	$	0.4	$	1.6	$	0.9