Condensed Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Millions	Jun. 30, 2018	Sep. 30, 2017
Statement of Financial Position [Abstract]
Allowance for doubtful accounts	$ 3.8	$ 2.2
Preferred stock, par value (USD per share)	$ 0.0001	$ 0.0001
Preferred shares authorized (in shares)	1,000,000	1,000,000
Preferred shares issued (in shares)	0	0
Preferred shares outstanding (in shares)	0	0
Common stock, par value (USD per share)	$ 0.0001	$ 0.0001
Shares authorized (in shares)	300,000,000	300,000,000
Shares issued (in shares)	89,753,662	89,353,641
Shares outstanding (in shares)	89,734,146	89,344,065
Treasury stock (in shares)	19,516	9,576

A valuation allowance for trade and other receivables due to an Entity within one year (or the normal operating cycle, whichever is longer) that are expected to be uncollectible.

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