Defined Benefit Pension and Other Postretirement Plans (Tables)

6 Months Ended

Mar. 31, 2019

Defined Benefit Plan [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 March 31,	2019			2018			2019			2018
Service cost	$	1,638		$	1,881		$	32		$	67
Interest cost	6,051			5,767			109			112
Expected return on assets	(8,140		)	(7,777		)	(184		)	(177		)
Amortization of:
Prior service cost (benefit)	62			63			(109		)	(110		)
Actuarial loss	1,721			2,984			17			24
Net benefit cost (benefit)	1,332			2,918			(135		)	(84		)
Change in associated regulatory liabilities	—			—			(342		)	(123		)
Net benefit cost (benefit) after change in regulatory liabilities	$	1,332		$	2,918		$	(477	)	$	(207	)
	Pension Benefits						Other Postretirement Benefits
Six Months Ended March 31,	2019			2018			2019			2018
Service cost	$	3,275		$	3,762		$	63		$	134
Interest cost	12,101			11,534			218			224
Expected return on assets	(16,280		)	(15,554		)	(369		)	(354		)
Amortization of:
Prior service cost (benefit)	125			126			(218		)	(220		)
Actuarial loss	3,441			5,968			34			48
Net benefit cost (benefit)	2,662			5,836			(272		)	(168		)
Change in associated regulatory liabilities	—			—			(685		)	(246		)
Net benefit cost (benefit) after change in regulatory liabilities	$	2,662		$	5,836		$	(957	)	$	(414	)