Equity-Based Compensation - Stock Option Activity (Details) - USD ($) $ / shares in Units, $ in Thousands	9 Months Ended
Jun. 30, 2018	Sep. 30, 2017
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Outstanding at beginning of period (shares)	0
Granted (shares)	2,045,000
Exercised (shares)	0
Forfeited (shares)	0
Outstanding at end of period (shares)	2,045,000
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price [Abstract]
Outstanding at beginning of period, weighted average exercise price (in USD per share)	$ 13.00	$ 0.00
Granted, weighted average exercise price (in USD per share)	13.00
Exercised, weighted average exercise price (in USD per share)	0.00
Forfeited, weighted average exercise price (in USD per share)	0.00
Outstanding at end of period, weighted average exercise price (in USD per share)	13.00	$ 0.00
Granted, weighted average grant date fair value (in USD per share)	$ 4.13
Options exercisable at end of period (shares)	0
Unrecognized compensation expense related to unvested options at end of period	$ 8,364
Period for recognition of unrecognized compensation cost	3 years

Weighted average period over which unrecognized compensation is expected to be recognized for equity-based compensation plans, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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- Definition

Unrecognized cost of unvested options awarded to employees as compensation.

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The number of shares into which fully or partially vested stock options outstanding as of the balance sheet date can be currently converted under the option plan.

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The number of shares under options that were cancelled during the reporting period as a result of occurrence of a terminating event specified in contractual agreements pertaining to the stock option plan.

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- Definition

Gross number of share options (or share units) granted during the period.

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No definition available.

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- Definition

The weighted average grant-date fair value of options granted during the reporting period as calculated by applying the disclosed option pricing methodology.

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- Definition

Number of options outstanding, including both vested and non-vested options.

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- Definition

A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

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- Definition

Weighted average price at which grantees can acquire the shares reserved for issuance under the stock option plan.

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- Definition

Weighted average price at which option holders acquired shares when converting their stock options into shares.

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- Definition

Weighted average price at which grantees could have acquired the underlying shares with respect to stock options that were terminated.

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- Definition

Weighted average per share amount at which grantees can acquire shares of common stock by exercise of options.

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- Definition

Number of share options (or share units) exercised during the current period.

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