Commitments and Contingencies, Legal Contingencies (Details) $ in Millions	1 Months Ended	12 Months Ended
	Jan. 31, 2019 USD ($)	Dec. 31, 2019 USD ($) MW
General Electric (GE) [Domain]
Loss Contingencies [Line Items]
Percentage of Fault		52.00%
NSP Minnesota [Member]
Loss Contingencies [Line Items]
Percentage of Fault		48.00%
Legal Contingencies [Abstract]
Customer refund of previously recovered purchased power costs	$ 20
Unregulated Operation [Member] | MEC Holdings LLC [Member]
Loss Contingencies [Line Items]
Natural Gas Combine Cycle Facility Output | MW		760
Property, Plant and Equipment, Additions		$ 650