Contracts with Customers - Summary of Contract Assets and Contract Liabilities (Parenthetical) (Details) - USD ($) $ in Millions	Sep. 30, 2021	Dec. 31, 2020
Revenue From Contract With Customer [Abstract]
Contract retentions	$ 94.3	$ 93.8
Contract retentions, not expected to be paid in next 12 months	52.3
Contract assets, unapproved change orders, claims, and requests	$ 106.0	$ 116.6

Amount of billed or unbilled claims or other similar items subject to uncertainty concerning their determination or ultimate realization under long-term contracts.

Reference 1: http://fasb.org/us-gaap/role/ref/otherTransitionRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 910
-SubTopic 10
-Section 50
-Paragraph 4
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=123353855&loc=SL119991585-234733

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(3)(c)(3))
-URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682

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