Accumulated Other Comprehensive Income (Tables)

9 Months Ended

Jun. 30, 2018

Equity [Abstract]

Schedule of Changes in Accumulated Other Comprehensive Income

The tables below present changes in AOCI, net of tax, during the three and nine months ended June 30, 2018 and 2017:

Three Months Ended June 30, 2018	Postretirement Benefit Plans			Derivative Instruments			Total
AOCI — March 31, 2018	$	(8,555	)	$	(16,612	)	$	(25,167	)
Reclassifications of benefit plan actuarial losses and net prior service credits	220			—			220
Reclassifications of net losses on IRPAs	—			592			592
AOCI — June 30, 2018	$	(8,335	)	$	(16,020	)	$	(24,355	)
Three Months Ended June 30, 2017	Postretirement Benefit Plans			Derivative Instruments			Total
AOCI — March 31, 2017	$	(11,356	)	$	(18,808	)	$	(30,164	)
Reclassifications of benefit plan actuarial losses and net prior service credits	239			—			239
Reclassifications of net losses on IRPAs	—			501			501
AOCI — June 30, 2017	$	(11,117	)	$	(18,307	)	$	(29,424	)

Nine Months Ended June 30, 2018	Postretirement Benefit Plans			Derivative Instruments			Total
AOCI — September 30, 2017	$	(8,995	)	$	(17,796	)	$	(26,791	)
Reclassifications of benefit plans actuarial losses and net prior service credits	660			—			660
Reclassifications of net losses on IRPAs	—			1,776			1,776
AOCI — June 30, 2018	$	(8,335	)	$	(16,020	)	$	(24,355	)
Nine Months Ended June 30, 2017	Postretirement Benefit Plans			Derivative Instruments			Total
AOCI — September 30, 2016	$	(11,834	)	$	(19,784	)	$	(31,618	)
Reclassifications of benefit plans actuarial losses and net prior service credits	717			—			717
Reclassifications of net losses on IRPAs	—			1,477			1,477
AOCI — June 30, 2017	$	(11,117	)	$	(18,307	)	$	(29,424	)