Commitments and Contingencies (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Loss Contingencies [Line Items]
Operating Leases, Rent Expense, Net	$ 1.1
Surety Bond [Member]
Loss Contingencies [Line Items]
Outstanding surety bonds	50.5	$ 52.1
Loss Contingency Portion Attributable to Work Remaining to Complete	20.3	24.4
Loans Payable [Member] | Corporate Joint Venture [Member]
Loss Contingencies [Line Items]
Related Party Transaction, Guarantor Obligations, Underlying Asset Class Guaranteed	7.3	6.7
Financial Guarantee [Member] | Corporate Joint Venture [Member]
Loss Contingencies [Line Items]
Long-term Debt, Gross	$ 41.3	$ 38.6