Commitments and Contingencies Commitments and Contingencies, Leases - Future Commitments (Details) - USD ($) $ in Millions	Jun. 30, 2019	Dec. 31, 2018
Operating Leases after Adoption of ASC Topic 842
2019	$ 24.8
2020	49.6
2021	49.5
2022	49.6
2023	49.6
Thereafter	505.6
Total minimum obligation	728.7
Interest component of obligation	(193.2)
Present value of minimum obligation	535.5
Less current portion	(26.5)
Noncurrent operating lease liabilities	$ 509.0	$ 0.0
Weighted-average remaining lease term in years	14 years 6 months
Operating Leases before Adoption of ASC 842
2019		51.9
2020		51.4
2021		51.3
2022		51.3
2023		51.3
Thereafter		507.1
PPAs
Operating Leases after Adoption of ASC Topic 842
2019	$ 23.1
2020	46.2
2021	46.2
2022	46.2
2023	46.2
Thereafter	450.8
Total minimum obligation	658.7
Interest component of obligation	(170.6)
Present value of minimum obligation	488.1
Operating Leases before Adoption of ASC 842
2019		46.7
2020		46.2
2021		46.2
2022		46.2
2023		46.2
Thereafter		450.8
Other
Operating Leases after Adoption of ASC Topic 842
2019	1.7
2020	3.4
2021	3.3
2022	3.4
2023	3.4
Thereafter	54.8
Total minimum obligation	70.0
Interest component of obligation	(22.6)
Present value of minimum obligation	$ 47.4
Operating Leases before Adoption of ASC 842
2019		5.2
2020		5.2
2021		5.1
2022		5.1
2023		5.1
Thereafter		$ 56.3