Defined Benefit Pension and Other Postretirement Plans (Tables)

9 Months Ended

Jun. 30, 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 relating to our employees include the following components:

	Pension Benefits						Other Postretirement Benefits
	Three Months Ended						Three Months Ended
	June 30,						June 30,
	2013			2012			2013			2012
Service cost	$	2,052		$	1,756		$	51		43
Interest cost	5,196			5,594			143			165
Expected return on assets	(6,197		)	(5,940		)	(133		)	(127		)
Amortization of:
Prior service cost (benefit)	62			62			(105		)	(105		)
Actuarial loss	3,366			1,963			91			99
Net benefit cost	4,479			3,435			47			75
Change in associated regulatory liabilities	—			—			815			784
Net expense	$	4,479		$	3,435		$	862		$	859
	Pension Benefits						Other Postretirement Benefits
	Nine Months Ended						Nine Months Ended
	June 30,						June 30,
	2013			2012			2013			2012
Service cost	$	6,158		$	5,269		$	154		$	129
Interest cost	15,587			16,782			428			497
Expected return on assets	(18,594		)	(17,822		)	(396		)	(380		)
Amortization of:
Prior service cost (benefit)	187			187			(317		)	(317		)
Actuarial loss	10,098			5,890			273			296
Net benefit cost	13,436			10,306			142			225
Change in associated regulatory liabilities	—			—			2,446			2,353
Net expense	$	13,436		$	10,306		$	2,588		$	2,578