Accounts Receivable, Net - Additional Information (Details) - USD ($) $ in Millions	Dec. 31, 2020	Sep. 30, 2020
Receivables [Abstract]
Accounts receivable	$ 346.2	$ 319.2
Allowance for doubtful accounts	4.6	2.8
Amounts of retention on incomplete project	$ 46.3	$ 45.9

Amount, after allowance for credit loss, of right to consideration from customer for product sold and service rendered in normal course of business, classified as current.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
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-SubTopic 10
-Section 45
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Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
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Reference 3: http://www.xbrl.org/2003/role/exampleRef
-Publisher FASB
-Name Accounting Standards Codification
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Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant