Stock-Based Compensation - Schedule of Share-based Payment Award, Employee Stock Purchase Plan, Valuation Assumptions (Details)	12 Months Ended
Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2018
Fair Value Assumptions
Expected dividend	0.00%	0.00%	0.00%
Expected term	6 months	6 months	6 months
Minimum
Fair Value Assumptions
Risk-free interest rate	1.10%	2.25%	1.14%
Expected volatility	26.32%	18.14%	22.03%
Maximum
Fair Value Assumptions
Risk-free interest rate	1.97%	2.51%	1.77%
Expected volatility	41.94%	31.74%	24.87%
Two Thousand Eleven Employee Stock Purchase Plan [Member]
Fair Value Assumptions
Expected term	6 months

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- Definition

The estimated dividend rate (a percentage of the share price) to be paid (expected dividends) to holders of the underlying shares over the option's term.

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- Definition

The estimated measure of the percentage by which a share price is expected to fluctuate during a period. Volatility also may be defined as a probability-weighted measure of the dispersion of returns about the mean. The volatility of a share price is the standard deviation of the continuously compounded rates of return on the share over a specified period. That is the same as the standard deviation of the differences in the natural logarithms of the stock prices plus dividends, if any, over the period.

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- Definition

The risk-free interest rate assumption that is used in valuing an option on its own shares.

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- Definition

Expected term of award under share-based payment arrangement, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days.

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-Name Accounting Standards Codification
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