Other Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Sep. 30, 2017
Other Liabilities [Line Items]
Net accrued retirement benefits, less amounts recognized within accrued liabilities	$ 54,396	$ 52,211
Noncurrent portion of deferred income from JV formation	235,855	236,896
Total unrecognized tax benefits, net of offsetting adjustments	20,003	20,949
Noncurrent income taxes payable	26,000	0
Acquired unfavorable contracts	1,562	2,076
Deferred economic incentives	14,337	14,574
Other	10,642	14,165
Other liabilities	366,268	344,798
Loss Reserve On Contractual Lease Commitments [Member]
Other Liabilities [Line Items]
Loss reserve	$ 3,473	$ 3,927