Defined Benefit Pension and Other Postretirement Plans (Tables)

9 Months Ended

Jun. 30, 2015

Defined Benefit Pension Plans and Defined Benefit Postretirement Plans Disclosure [Abstract]

Components of Net Periodic Pension Expense and Other Postretirement Benefit Costs

Net periodic pension expense and other postretirement benefit costs include the following components:

	Pension Benefits						Other Postretirement Benefits
Three Months Ended June 30,	2015			2014			2015			2014
Service cost	$	2.5		$	2.3		$	0.2		$	0.1
Interest cost	6.2			6.5			0.2			0.2
Expected return on assets	(7.9		)	(7.3		)	(0.2		)	(0.1		)
Amortization of:
Prior service cost (benefit)	—			0.1			(0.2		)	(0.1		)
Actuarial loss	2.5			1.9			0.1			—
Net benefit cost	3.3			3.5			0.1			0.1
Change in associated regulatory liabilities	—			—			0.9			0.9
Net expense	$	3.3		$	3.5		$	1.0		$	1.0
	Pension Benefits						Other Postretirement Benefits
Nine Months Ended June 30,	2015			2014			2015			2014
Service cost	$	7.4		$	7.0		$	0.5		$	0.4
Interest cost	18.8			19.4			0.6			0.7
Expected return on assets	(23.8		)	(22.0		)	(0.5		)	(0.4		)
Amortization of:
Prior service cost (benefit)	0.2			0.2			(0.4		)	(0.4		)
Actuarial loss	7.5			5.7			0.1			0.1
Net benefit cost	10.1			10.3			0.3			0.4
Change in associated regulatory liabilities	—			—			2.8			2.7
Net expense	$	10.1		$	10.3		$	3.1		$	3.1