Fair Value of Financial Assets and Liabilities Commodity Derivatives (Details) MWh in Millions, MMBTU in Millions, $ in Millions		Dec. 31, 2019 USD ($) MMBTU MWh	Dec. 31, 2018 MMBTU MWh
Derivative [Line Items]
Commodity contracts designated as cash flow hedges | $		$ 0.0
Electric Commodity
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount | MWh	[1],[2]	79.1	56.8
Natural Gas Commodity
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount | MMBTU	[1],[2]	77.8	42.7

[1] Amounts are not reflective of net positions in the underlying commodities.

[2] Notional amounts for options are included on a gross basis, but are weighted for the probability of exercise.