Long-Term Borrowings - Summary of Long-Term Borrowings (Details) - USD ($) $ in Thousands	Jun. 30, 2018	Sep. 30, 2017
Debt Instrument [Line Items]
Long-term borrowings	$ 1,276,145	$ 1,287,645
Less: unamortized debt issuance costs	(13,967)	(15,481)
Long-term borrowings	1,262,178	1,272,164
5.5% Senior Notes due June 1, 2024 [Member]
Debt Instrument [Line Items]
Long-term borrowings	525,000	525,000
5.75% Senior Notes due March 1, 2025 [Member]
Debt Instrument [Line Items]
Long-term borrowings	250,000	250,000
5.875% Senior Notes due March 1, 2027 [Member]
Debt Instrument [Line Items]
Long-term borrowings	350,000	350,000
Revolving Credit Facility due March 3, 2021 [Member]
Debt Instrument [Line Items]
Long-term borrowings	$ 151,145	$ 162,645

Amount, before unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but is not limited to, notes payable, bonds payable, commercial loans, mortgage loans, convertible debt, subordinated debt and other types of debt.

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Amount, after accumulated amortization, of debt issuance costs. Includes, but is not limited to, legal, accounting, underwriting, printing, and registration costs.

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Amount after unamortized (discount) premium and debt issuance costs of long-term debt classified as noncurrent and excluding amounts to be repaid within one year or the normal operating cycle, if longer. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

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