Commitments and Contingencies - Narrative (Details)				1 Months Ended
	Dec. 20, 2018 USD ($)	Nov. 03, 2017 USD ($) plaintiff	Feb. 07, 2017 plaintiff	Jan. 31, 2019 USD ($)	Jan. 31, 2018 USD ($)	Apr. 30, 2019 USD ($)
Loss Contingencies [Line Items]
Standby letters of credit						$ 152,400,000
Surety bonds						$ 556,300,000
Subsidiary ownership interest (in percent)						33.00%
Loss contingency amount accrued for probable losses						$ 11,700,000
Energy Savings Contracts
Loss Contingencies [Line Items]
Guarantee obligation						175,300,000
Performance Guarantee | Joint Venture
Loss Contingencies [Line Items]
Total guarantees						35,000,000
Minimum
Loss Contingencies [Line Items]
Amount of reasonably possible loss						0
Maximum
Loss Contingencies [Line Items]
Amount of reasonably possible loss						7,000,000
Settled Litigation | Hussein
Loss Contingencies [Line Items]
Loss contingency amount accrued for probable losses						1,200,000
Settlement amount	$ 2,100,000
Settled Litigation | Isse
Loss Contingencies [Line Items]
Number of plaintiffs | plaintiff		220	60
Payments for legal settlements					$ 4,500,000
Settled Litigation | Hussein And Isse
Loss Contingencies [Line Items]
Settlement amount		$ 8,300,000
Settled Litigation | Hussein, Opt-Out
Loss Contingencies [Line Items]
Settlement amount				$ 1,200,000
Pending Litigation | Castro
Loss Contingencies [Line Items]
Loss contingency amount accrued for probable losses						$ 5,400,000