Fair Value of Financial Instruments Fair Value Options Quantitative Disclosure (Details) - USD ($)	Jun. 30, 2020	Dec. 31, 2019
Low [Member]
Commodity Contracts
Electricity physical forwards	$ 2.69	$ 12.53
Natural gas financial swaps	1.44	1.39
Financial swaps - electricity	13.25	10.57
High [Member]
Commodity Contracts
Electricity physical forwards	38.84	59.00
Natural gas financial swaps	3.91	3.73
Financial swaps - electricity	51.03	66.32
Weighted Average [Member]
Commodity Contracts
Electricity physical forwards	29.51	36.92
Natural gas financial swaps	2.12	1.90
Financial swaps - electricity	36.29	45.11
Assets [Member]
Commodity Contracts
Electricity physical forwards	0	0
Natural gas financial swaps	3,000,000	1,000,000
Financial swaps - electricity	0	7,000,000
Total commodity contracts	3,000,000	8,000,000
Liabilities [Member]
Commodity Contracts
Electricity physical forwards	147,000,000	104,000,000
Natural gas financial swaps	0	0
Financial swaps - electricity	7,000,000	1,000,000
Total commodity contracts	$ 154,000,000	$ 105,000,000