Accounting Standards and Significant Accounting Policies - Additional Information (Details) - USD ($) $ in Millions	Sep. 30, 2019	Dec. 31, 2018
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Accounts receivable, net	$ 368.4	$ 314.9
Unbilled Revenues
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Accounts receivable, net	126.5	104.2
Retention Receivable | Unbilled Revenues
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Accounts receivable, net	$ 12.9	$ 12.2