Commitments and Contingencies - Narrative (Details)	Sep. 20, 2018 subclass	Apr. 30, 2020 USD ($)
Loss Contingencies [Line Items]
Standby letters of credit		$ 153,100,000
Subsidiary ownership interest (in percent)		33.00%
Surety Bonds
Loss Contingencies [Line Items]
Surety bonds		$ 575,900,000
Energy Savings Contracts
Loss Contingencies [Line Items]
Guarantee obligation		183,600,000
Performance Guarantee | Joint Venture
Loss Contingencies [Line Items]
Total guarantees		41,000,000
Minimum
Loss Contingencies [Line Items]
Amount of reasonably possible loss		0
Maximum
Loss Contingencies [Line Items]
Amount of reasonably possible loss		12,000,000
Bucio
Loss Contingencies [Line Items]
Loss Contingency, Number Of Certified Subclasses | subclass	4
Pending Litigation
Loss Contingencies [Line Items]
Loss contingency amount accrued for probable losses		$ 6,800,000