Accumulated Other Comprehensive Income - Schedule of Accumulated Other Comprehensive Income (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2013
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	$ (8,181)	$ (8,720)
Reclassifications, net of tax	517	385
Net (losses) gains on derivative instruments	(4,105)	0	$ 15,153
Benefit plans, principally actuarial losses	(3,482)	(1,413)	4,689
Ending balance	(13,686)	(8,181)	(8,720)
Postretirement Benefit Plans
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(6,311)	(5,283)
Reclassifications, net of tax	517	385
Net (losses) gains on derivative instruments	0
Benefit plans, principally actuarial losses	(3,482)	(1,413)
Ending balance	(9,276)	(6,311)	(5,283)
Derivative Instrument Net Losses
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(1,870)	(3,437)
Reclassifications, net of tax	0	0
Net (losses) gains on derivative instruments	(4,105)
Benefit plans, principally actuarial losses	0	0
Ending balance	(4,410)	(1,870)	$ (3,437)
Interest Rate Protection Agreements
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Reclassifications, net of tax	1,565	1,567
Interest Rate Protection Agreements | Postretirement Benefit Plans
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Reclassifications, net of tax	0	0
Interest Rate Protection Agreements | Derivative Instrument Net Losses
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Reclassifications, net of tax	$ 1,565	$ 1,567