Commitments and Contingencies - Narrative (Details) $ in Millions	3 Months Ended
	Mar. 31, 2019 USD ($)
Other Commitments [Line Items]
Purchase orders outstanding	$ 10.0
Performance Guarantee [Member]
Other Commitments [Line Items]
Bonds outstanding	646.1
Estimated remaining costs for bonded projects	320.0
Contingencies Excluding Wildfire and Health Insurance [Member]
Other Commitments [Line Items]
Insurance coverage deductible	1.0
Wildfire [Member]
Other Commitments [Line Items]
Insurance coverage deductible	2.0
Health Insurance [Member]
Other Commitments [Line Items]
Insurance coverage deductible	$ 0.2