Condensed Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Millions	Jun. 30, 2020	Dec. 31, 2019
Statement of Financial Position [Abstract]
Allowance for credit losses and allowance for doubtful accounts on Accounts receivable and retention	$ 4.1	$ 0.4
Allowance for credit losses and allowance for doubtful accounts on Other receivables	4.3	1.6
Allowance for credit losses and allowance for doubtful accounts on Prepaid expenses and other assets	$ 0.1	$ 0.0
Common stock authorized (shares)	150,000,000	150,000,000
Common stock outstanding (shares)	72,300,000	72,300,000