Defined Benefit Pension and Other Postretirement Plans (Tables)

6 Months Ended

Mar. 31, 2013

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

Component 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 March 31,						Three Months Ended March 31,
	2013			2012			2013			2012
Service cost	$	2.8		$	2.1		$	0.2		$	0.1
Interest cost	5.9			6.1			0.2			0.2
Expected return on assets	(6.9		)	(6.4		)	(0.1		)	(0.1		)
Amortization of:
Prior service cost (benefit)	0.1			0.1			(0.1		)	(0.1		)
Actuarial loss	3.7			2.1			0.1			0.1
Net benefit cost	5.6			4.0			0.3			0.2
Change in associated regulatory liabilities	—			—			0.8			0.8
Net expense	$	5.6		$	4.0		$	1.1		$	1.0
	Pension Benefits						Other Postretirement Benefits
	Six Months Ended						Six Months Ended
	March 31,						March 31,
	2013			2012			2013			2012
Service cost	$	5.7		$	4.3		$	0.3		$	0.2
Interest cost	11.8			12.2			0.5			0.5
Expected return on assets	(13.8		)	(12.8		)	(0.3		)	(0.3		)
Amortization of:
Prior service cost (benefit)	0.2			0.1			(0.1		)	(0.2		)
Actuarial loss	7.4			4.2			0.2			0.2
Net benefit cost	11.3			8.0			0.6			0.4
Change in associated regulatory liabilities	—			—			1.6			1.6
Net expense	$	11.3		$	8.0		$	2.2		$	2.0