Debt, net - Additional Information (Detail) - USD ($) $ in Millions	9 Months Ended
Jun. 30, 2019	Sep. 30, 2018
Debt Instrument [Line Items]
Line of Credit Facility, Current Borrowing Capacity	$ 380.0
Line of Credit Facility, Accordion Amount	190.0
Line of Credit Facility, Maximum Borrowing Capacity	$ 570.0
Letter of Credit, Maximum Borrowing Capacity	50.00%
Proceeds from Long-term Lines of Credit	$ 85.0
Long-term Line of Credit	0.0	$ 0.0
Line of Credit Facility, Remaining Borrowing Capacity	358.3
Senior Notes [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount	$ 350.0
Effective interest rate of liability component	8.50%
Interest rate percentage	8.00%	8.00%
Debt Instrument, Maturity Date	Apr. 15, 2024
Deferred finance costs, net	$ 6.6
3.75% convertible senior notes due 2020, net of discount
Debt Instrument [Line Items]
Debt Instrument, Face Amount	118.9
Debt Instrument, Unamortized Discount	$ 3.1
Effective interest rate of liability component	8.00%
Debt Instrument, Convertible, Carrying Amount of Equity Component	$ 16.8
Interest rate percentage	3.75%	3.75%
Debt Instrument, Maturity Date	Mar. 01, 2020
Deferred finance costs, net	$ 0.3	$ 0.7
Line of Credit [Member]
Debt Instrument [Line Items]
Letters of credit outstanding	$ 21.7

Maximum borrowing capacity of letter of credit.

No definition available.

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- Definition

The amount by which the capacity of a credit facility can be increased as a result of its accordion feature.

+ References

No definition available.

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- Definition

The carrying amount of the equity component of convertible debt which may be settled in cash upon conversion.

+ References

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 20
-Section 50
-Paragraph 4
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- Definition

Face (par) amount of debt instrument at time of issuance.

+ References

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- Definition

Effective interest rate for the funds borrowed under the debt agreement considering interest compounding and original issue discount or premium.

+ References

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- Definition

Contractual interest rate for funds borrowed, under the debt agreement.

+ References

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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.

+ References

No definition available.

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- Definition

Date when the debt instrument is scheduled to be fully repaid, in CCYY-MM-DD format.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
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- Definition

Amount, after accumulated amortization, of debt discount.

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- Definition

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

+ References

+ Details

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- Definition

The total amount of the contingent obligation under letters of credit outstanding as of the reporting date.

+ References

No definition available.

+ Details

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- Definition

The carrying value as of the balance sheet date of the current and noncurrent portions of long-term obligations drawn from a line of credit, which is a bank's commitment to make loans up to a specific amount. Examples of items that might be included in the application of this element may consist of letters of credit, standby letters of credit, and revolving credit arrangements, under which borrowings can be made up to a maximum amount as of any point in time conditional on satisfaction of specified terms before, as of and after the date of drawdowns on the line. Includes short-term obligations that would normally be classified as current liabilities but for which (a) postbalance sheet date issuance of a long term obligation to refinance the short term obligation on a long term basis, or (b) the enterprise has entered into a financing agreement that clearly permits the enterprise to refinance the short-term obligation on a long term basis and the following conditions are met (1) the agreement does not expire within 1 year and is not cancelable by the lender except for violation of an objectively determinable provision, (2) no violation exists at the BS date, and (3) the lender has entered into the financing agreement is expected to be financially capable of honoring the agreement.

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- Definition

Amount of current borrowing capacity under the credit facility considering any current restrictions on the amount that could be borrowed (for example, borrowings may be limited by the amount of current assets), but without considering any amounts currently outstanding under the facility.

+ References

+ Details

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- Definition

Maximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility.

+ References

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- Definition

Amount of borrowing capacity currently available under the credit facility (current borrowing capacity less the amount of borrowings outstanding).

+ References

+ Details

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- Definition

The cash inflow from a contractual arrangement with the lender, including letter of credit, standby letter of credit and revolving credit arrangements, under which borrowings can be made up to a specific amount at any point in time with maturities due beyond one year or the operating cycle, if longer.

+ References

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