Defined Benefit Pension and Other Postretirement Plans (Tables)

9 Months Ended

Jun. 30, 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 June 30,	2019			2018			2019			2018
Service cost	$	1,637		$	1,882		$	31		$	66
Interest cost	6,050			5,766			109			111
Expected return on assets	(8,140		)	(7,776		)	(185		)	(178		)
Amortization of:
Prior service cost (benefit)	63			61			(109		)	(110		)
Actuarial loss	1,721			2,984			17			23
Net benefit cost (benefit)	1,331			2,917			(137		)	(88		)
Change in associated regulatory liabilities	—			—			(343		)	(122		)
Net benefit cost (benefit) after change in regulatory liabilities	$	1,331		$	2,917		$	(480	)	$	(210	)
	Pension Benefits						Other Postretirement Benefits
Nine Months Ended June 30,	2019			2018			2019			2018
Service cost	$	4,912		$	5,644		$	94		$	200
Interest cost	18,151			17,300			327			335
Expected return on assets	(24,420		)	(23,330		)	(554		)	(532		)
Amortization of:
Prior service cost (benefit)	188			187			(327		)	(330		)
Actuarial loss	5,162			8,952			51			71
Net benefit cost (benefit)	3,993			8,753			(409		)	(256		)
Change in associated regulatory liabilities	—			—			(1,028		)	(368		)
Net benefit cost (benefit) after change in regulatory liabilities	$	3,993		$	8,753		$	(1,437	)	$	(624	)