Summary of Significant Accounting Policies - Narrative (Details) - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2014	Oct. 24, 2011
Significant Accounting Policies [Line Items]
Advertising costs incurred	$ 17,200	$ 16,500	$ 19,400
Total comprehensive income (loss), net of taxes	203,900	(181,449)	(136,204)
Foreign currency transaction gains (losses)	$ (800)	$ (1,100)	$ (1,400)
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount	1,047	528	328
Sales and marketing	$ 303,503	$ 311,712	$ 324,370
2.75% Convertible Debentures due November 1, 2031
Significant Accounting Policies [Line Items]
Convertible debentures, interest rate	2.75%	2.75%		2.75%	2.75%

Significant Accounting Policies [Line Items]

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- Definition

Amount charged to advertising expense for the period, which are expenses incurred with the objective of increasing revenue for a specified brand, product or product line.

+ References

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Securities (including those issuable pursuant to contingent stock agreements) that could potentially dilute basic earnings per share (EPS) or earnings per unit (EPU) in the future that were not included in the computation of diluted EPS or EPU because to do so would increase EPS or EPU amounts or decrease loss per share or unit amounts for the period presented.

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Amount after tax of increase (decrease) in equity from transactions and other events and circumstances from net income and other comprehensive income, attributable to parent entity. Excludes changes in equity resulting from investments by owners and distributions to owners.

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

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Amount before tax of foreign currency transaction realized gain (loss) recognized in the income statement.

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The aggregate total amount of expenses directly related to the marketing or selling of products or services.

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