Fair Value of Financial Assets and Liabilities Commodity Derivatives (Details) MWh in Millions, MMBTU in Millions, $ in Millions		Mar. 31, 2020 USD ($) MMBTU MWh	Dec. 31, 2019 MMBTU MWh
Cash flow hedge commodity [Member]
Derivative [Line Items]
Commodity contracts designated as cash flow hedges | $		$ 0.0
Electric Commodity [Member]
Gross Notional Amounts of Commodity Forwards and Options [Abstract]
Derivative, Nonmonetary Notional amount | MWh	[1],[2]	9.4	9.3
Natural Gas Commodity [Member]
Gross Notional Amounts of Commodity Forwards and Options [Abstract]
Derivative, Nonmonetary Notional amount | MMBTU	[1],[2]	50.4	32.2

[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.