Defined Benefit Pension and Other Postretirement Plans (Tables)

3 Months Ended

Dec. 31, 2015

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

Schedule of 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 December 31,	2015			2014			2015			2014
Service cost	$	1,732		$	1,741		$	46		$	48
Interest cost	5,817			5,627			116			119
Expected return on assets	(7,167		)	(7,224		)	(149		)	(153		)
Amortization of:
Prior service cost (benefit)	87			87			(160		)	(160		)
Actuarial loss	2,393			2,198			24			32
Net benefit cost (income)	2,862			2,429			(123		)	(114		)
Change in associated regulatory liabilities	—			—			878			937
Net benefit cost after change in regulatory liabilities	$	2,862		$	2,429		$	755		$	823