Retirement Benefits

6 Months Ended

Mar. 31, 2018

Retirement Benefits [Abstract]

Retirement Benefits

Retirement Benefits

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

	Pension Benefits
	Three Months Ended March 31,						Six Months Ended March 31,
	2018			2017			2018			2017
Service cost	$	22.4		$	24.2		$	44.6		$	48.3
Interest cost	39.0			37.8			77.8			75.6
Expected return on plan assets	(61.5		)	(56.2		)	(122.7		)	(112.4		)
Amortization:
Prior service cost (credit)	0.1			(1.1		)	0.3			(1.9		)
Net actuarial loss	28.4			38.2			56.7			76.2
Settlements	—			—			—			0.2
Net periodic benefit cost	$	28.4		$	42.9		$	56.7		$	86.0

	Other Postretirement Benefits
	Three Months Ended March 31,						Six Months Ended March 31,
	2018			2017			2018			2017
Service cost	$	0.3		$	0.4		$	0.6		$	0.7
Interest cost	0.6			0.7			1.2			1.3
Amortization:
Prior service credit	(1.4		)	(1.5		)	(2.7		)	(3.0		)
Net actuarial loss	0.5			0.6			0.9			1.1
Net periodic benefit cost	$	—		$	0.2		$	—		$	0.1