Commitments and Contingencies Commitments and Contingencies, Leases - Components of Lease Expense (Details) $ in Millions	3 Months Ended	6 Months Ended
	Jun. 30, 2019 USD ($)	Jun. 30, 2019 USD ($)
Lessee, Lease, Description [Line Items]
Operating Lease, Weighted Average Discount Rate, Percent	4.40%	4.40%
Operating Lease, Cost	$ 13.9	$ 27.9
Short-term Lease, Cost	0.5	0.9
PPAs
Lessee, Lease, Description [Line Items]
Operating Lease, Cost	12.6	25.4
Other
Lessee, Lease, Description [Line Items]
Operating Lease, Cost	$ 1.3	$ 2.5