Other Liabilities (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Sep. 30, 2017
Other Liabilities [Line Items]
Net accrued retirement benefits, less amounts recognized within accrued liabilities	$ 90,722	$ 52,211
Noncurrent portion of deferred income from JV formation	235,300	236,896
Total unrecognized tax benefits, net of offsetting adjustments	8,582	20,949
Noncurrent income taxes payable	12,494	0
Acquired unfavorable contracts	54	2,076
Deferred economic incentives	13,038	14,574
Loss reserve, noncurrent portion	2,686	3,927
Derivative liability	23,000	0
Other	12,179	14,165
Other liabilities	398,055	$ 344,798
Loss Reserve On Contractual Lease Commitments [Member]
Other Liabilities [Line Items]
Loss reserve, noncurrent portion	$ 2,686