Construction Contracts (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Capitalized contract cost, amortization	$ 0.7	$ 0.1
Construction receivables retentions	16.6		$ 9.0
Construction
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Retentions	18.6		18.0
Portion Attributable To Pending Contracts
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Deferred pre-contract costs	$ 1.2		$ 0.9