Borrowings and Other Financing Instruments Preferred Stock (Details) - PSCo [Member] - $ / shares	Dec. 31, 2020	Dec. 31, 2019
Preferred Stock [Abstract]
Preferred Stock, Shares Authorized	10,000,000
Preferred Stock, Par or Stated Value Per Share	$ 0.01
Preferred stock, shares outstanding (in shares)	0	0
Debt Instrument [Line Items]
Preferred Stock, Shares Authorized	10,000,000
Preferred Stock, Par or Stated Value Per Share	$ 0.01
Preferred stock, shares outstanding (in shares)	0	0