Defined Benefit Pension and Other Postretirement Plans (Tables)

3 Months Ended

Dec. 31, 2012

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
	December 31,						December 31,
	2012			2011			2012			2011
Service cost	$	2,053		$	1,756		$	51		$	43
Interest cost	5,196			5,594			143			166
Expected return on assets	(6,198		)	(5,940		)	(132		)	(127		)
Amortization of:
Prior service cost (benefit)	—			62			(105		)	(106		)
Actuarial loss	3,428			1,963			91			99
Net benefit cost	4,479			3,435			48			75
Change in associated regulatory liabilities	—			—			815			784
Net expense	$	4,479		$	3,435		$	863		$	859