Debt - Interest Rate Contracts (Details) - Cash Flow Hedging - Designated as Hedging Instrument - Interest rate swap contracts - USD ($) |
6 Months Ended | 12 Months Ended |
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Mar. 31, 2018 |
Sep. 30, 2017 |
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| Derivative [Line Items] | ||
| Pay fixed swaps - notional amount | $ 404,688,000 | $ 414,063,000 |
| Net unrealized gain | $ 9,912,000 | $ 3,959,000 |
| Weighted-average maturity period (years) | 2 years 9 months 24 days | 3 years 3 months 24 days |
| Weighted-average received rate (as a percent) | 1.88% | 1.23% |
| Weighted-average pay rate (as a percent) | 1.35% | 1.34% |
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- Definition Aggregate notional amount specified by the derivative(s). Expressed as an absolute value. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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- Definition Average fixed interest rate related to the group of interest rate derivatives. No definition available.
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- Definition Average remaining period until maturity of the derivative contract, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. No definition available.
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- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. No definition available.
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- Definition Variable interest rate in effect as of the balance sheet date related to the interest rate derivative. No definition available.
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- Definition The net change in the difference between the fair value and the carrying value, or in the comparative fair values, of derivative instruments, including options, swaps, futures, and forward contracts, held at each balance sheet date, that was included in earnings for the period. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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