Retirement Benefits (Tables)

6 Months Ended

Mar. 31, 2019

Retirement Benefits [Abstract]

Schedule of Net Benefit Costs

The components of net periodic benefit cost are (in millions):

	Pension Benefits
	Three Months Ended March 31,						Six Months Ended March 31,
	2019			2018			2019			2018
Service cost	$	19.5		$	22.4		$	39.1		$	44.6
Interest cost	39.6			39.0			79.2			77.8
Expected return on plan assets	(61.2		)	(61.5		)	(122.4		)	(122.7		)
Amortization:
Prior service cost	0.3			0.1			0.6			0.3
Net actuarial loss	19.5			28.4			39.0			56.7
Settlements	(0.2		)	—			(0.4		)	—
Net periodic benefit cost	$	17.5		$	28.4		$	35.1		$	56.7

	Other Postretirement Benefits
	Three Months Ended March 31,						Six Months Ended March 31,
	2019			2018			2019			2018
Service cost	$	0.3		$	0.3		$	0.5		$	0.6
Interest cost	0.5			0.6			1.1			1.2
Amortization:
Prior service credit	(1.3		)	(1.4		)	(2.7		)	(2.7		)
Net actuarial loss	0.2			0.5			0.4			0.9
Net periodic benefit credit	$	(0.3	)	$	—		$	(0.7	)	$	—