Summary of Significant Accounting Policies - AFUDC (Details)		12 Months Ended
	Dec. 19, 2017	Dec. 31, 2020
Regulatory Assets [Line Items]
Public Utilities, Property, Plant and Equipment, Non-project Electric Utility Plant, Estimated Useful Life Average		30 years
Subsidiaries [Member]
Regulatory Assets [Line Items]
Regulated Utility, Allowed Rate of Return on Net Regulatory Assets and Liabilities	7.60%