Long-Term Debt - Capital Leases (Details) - USD ($)		6 Months Ended
	Mar. 20, 2012	Mar. 31, 2017	Sep. 30, 2016
Debt Instrument [Line Items]
Outstanding capital lease obligations		$ 14,000,000	$ 16,000,000
Financing Arrangements For Capital Leases
Debt Instrument [Line Items]
Maximum amount of progress payments for equipment under construction	$ 10,000,000
Financing Arrangements For Capital Leases | Five-Year Swap Rate
Debt Instrument [Line Items]
Basis spread on variable rate		5.64%
Capital Lease Arrangements
Debt Instrument [Line Items]
Capital lease, term	60 months
Outstanding capital lease obligations		$ 4,000,000	7,000,000
Capital Lease Arrangements | 30-Day LIBOR
Debt Instrument [Line Items]
Basis spread on variable rate		4.75%
Other Capital Lease Arrangements
Debt Instrument [Line Items]
Outstanding capital lease obligations		$ 10,000,000	$ 9,000,000