Accounts Receivable, net	6 Months Ended
Mar. 31, 2021
Receivables [Abstract]
Accounts Receivable, net	4.Accounts Receivable, net Accounts receivable of $376.4 and $319.2, is net of an allowance for doubtful accounts of $7.0 and $2.8 and includes $42.5 and $45.9 of retention on incomplete projects to be completed within one year at March 31, 2021 and September 30, 2020, respectively.

The entire disclosure for accounts receivable, contract receivable, receivable held-for-sale, and nontrade receivable.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-URI http://asc.fasb.org/topic&trid=2196771

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-URI http://asc.fasb.org/topic&trid=82887179

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