Income Taxes (Details)		3 Months Ended
		Mar. 31, 2021	Mar. 31, 2020	[1]
Income Tax Disclosure [Abstract]
Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent		21.00%	21.00%
Effective Income Tax Rate Reconciliation, State and Local Income Taxes, Percent		7.00%	7.10%
Effective Income Tax Rate Reconciliation, Tax Credit, Percent		(30.40%)	(24.80%)
Plant regulatory differences	[2]	(7.80%)	(8.30%)
Effective Income Tax Rate Reconciliation,Other Reconciling Items, Percent		(1.30%)	(1.50%)
Effective Income Tax Rate Reconciliation, Other Adjustments, Percent		1.20%	0.60%
Effective Income Tax Rate Reconciliation, Percent, Total		(10.30%)	(5.90%)

[1]     Prior periods have been restated to conform to current year presentation.

[2] Regulatory differences for income tax primarily relate to the credit of excess deferred taxes to customers through the average rate assumption method. Income tax benefits associated with the credit of excess deferred credits are offset by corresponding revenue reduction.